ARC: SuSv3 legacy support: Add "bcmp" alias for memcmp

Although uClibc provides this already as UCLIBC_SUSV3_LEGACY_MACROS,
that however requires UCLIBC_SUSV3_LEGACY to be switched off, causing a
bunch of other things to be not available (usleep)

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