ARC: unaligned: relax the check for gcc supporting -mno-unaligned-access

Without bleeding edge gcc, kernel builds were tripping everywhere.

So current gcc will generate unaligned code despite
!CONFIG_ARC_USE_UNALIGNED_MEM_ACCESS but that is something we have to
live with.

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>