ARM: only allow kernel mode neon with AEABI

This prevents the linker erroring with:

arm-linux-ld: error: arch/arm/lib/xor-neon.o uses VFP instructions, whereas arch/arm/lib/built-in.o does not
arm-linux-ld: failed to merge target specific data of file arch/arm/lib/xor-neon.o

This is due to the non-neon files being marked as containing FPA data/
instructions (even though they do not) being mixed with files which
contain VFP, which is an incompatible floating point format.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

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https://github.com/faux123/htc-m7/commit/50552c4a6c8817da58034cfc39df1db8bff71004