mips_malta: fix copy of the 0x1fc00000 region

Copy the whole 0x1fe000000 region into 0x1fc00000, independently of the
loaded BIOS size. This fix the MIPS make check tests.

Reported-by: Andreas Färber <afaerber@suse.de>
Tested-by: Andreas Färber <afaerber@suse.de>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: Leon Alrae <leon.alrae@imgtec.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
