scsi-bus: remove duplicate table entries

Remove duplicate entries from SCSI command table, spotted by
clang analyzer:
/src/qemu/hw/scsi-bus.c:979:40: warning: initializer overrides prior initialization of this subobject
        [ ERASE_16                 ] = "ERASE_16",
/src/qemu/hw/scsi-bus.c:978:40: note: previous initialization is here
        [ WRITE_SAME_16            ] = "WRITE_SAME_16",
/src/qemu/hw/scsi-bus.c:984:40: warning: initializer overrides prior initialization of this subobject
        [ MAINTENANCE_IN           ] = "MAINTENANCE_IN",
/src/qemu/hw/scsi-bus.c:917:40: note: previous initialization is here
        [ MAINTENANCE_IN           ] = "MAINTENANCE_IN",
/src/qemu/hw/scsi-bus.c:985:40: warning: initializer overrides prior initialization of this subobject
        [ MAINTENANCE_OUT          ] = "MAINTENANCE_OUT",
/src/qemu/hw/scsi-bus.c:918:40: note: previous initialization is here
        [ MAINTENANCE_OUT          ] = "MAINTENANCE_OUT",

Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
