scsi: qedi: remove memset/memcpy to nfunc and use func instead

KASAN reports this:

BUG: KASAN: global-out-of-bounds in qedi_dbg_err+0xda/0x330 [qedi]
Read of size 31 at addr ffffffffc12b0ae0 by task syz-executor.0/2429

CPU: 0 PID: 2429 Comm: syz-executor.0 Not tainted 5.0.0-rc7+ #45
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0xfa/0x1ce lib/dump_stack.c:113
 print_address_description+0x1c4/0x270 mm/kasan/report.c:187
 kasan_report+0x149/0x18d mm/kasan/report.c:317
 memcpy+0x1f/0x50 mm/kasan/common.c:130
 qedi_dbg_err+0xda/0x330 [qedi]
 ? 0xffffffffc12d0000
 qedi_init+0x118/0x1000 [qedi]
 ? 0xffffffffc12d0000
 ? 0xffffffffc12d0000
 ? 0xffffffffc12d0000
 do_one_initcall+0xfa/0x5ca init/main.c:887
 do_init_module+0x204/0x5f6 kernel/module.c:3460
 load_module+0x66b2/0x8570 kernel/module.c:3808
 __do_sys_finit_module+0x238/0x2a0 kernel/module.c:3902
 do_syscall_64+0x147/0x600 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x462e99
Code: f7 d8 64 89 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f2d57e55c58 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
RAX: ffffffffffffffda RBX: 000000000073bfa0 RCX: 0000000000462e99
RDX: 0000000000000000 RSI: 00000000200003c0 RDI: 0000000000000003
RBP: 00007f2d57e55c70 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f2d57e566bc
R13: 00000000004bcefb R14: 00000000006f7030 R15: 0000000000000004

The buggy address belongs to the variable:
 __func__.67584+0x0/0xffffffffffffd520 [qedi]

Memory state around the buggy address:
 ffffffffc12b0980: fa fa fa fa 00 04 fa fa fa fa fa fa 00 00 05 fa
 ffffffffc12b0a00: fa fa fa fa 00 00 04 fa fa fa fa fa 00 05 fa fa
> ffffffffc12b0a80: fa fa fa fa 00 06 fa fa fa fa fa fa 00 02 fa fa
                                                          ^
 ffffffffc12b0b00: fa fa fa fa 00 00 04 fa fa fa fa fa 00 00 03 fa
 ffffffffc12b0b80: fa fa fa fa 00 00 02 fa fa fa fa fa 00 00 04 fa

Currently the qedi_dbg_* family of functions can overrun the end of the
source string if it is less than the destination buffer length because of
the use of a fixed sized memcpy. Remove the memset/memcpy calls to nfunc
and just use func instead as it is always a null terminated string.

Reported-by: Hulk Robot <hulkci@huawei.com>
Fixes: ace7f46ba5fd ("scsi: qedi: Add QLogic FastLinQ offload iSCSI driver framework.")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
