The bsaes-armv7.S asm has an #if __ARM_ARCH__>=7 around its contents,
i.e. it's not just switched at runtime – it only compiles for >= ARMv7.
I mistakenly regressed e_aes.c in 3e652657 to always expected bsaes
functions to exist on ARM. This change fixes that.
Change-Id: Ifd9111438508909a0627b25aee3e2f11e62e3ee8