broadcom/vc4: Build the vc4_tiling_lt_neon.c with -mfpu=neon on ARM.

broadcom/vc4: Build the vc4_tiling_lt_neon.c with -mfpu=neon on ARM.

If you don't pass this, the compiler refuses to compile the assembly for
pre-v7 CPUs.  This also keeps us from building identical, non-NEON code on
aarch64 and x86.

Fixes: a373f77662c5 ("vc4: Use a wrapper file to set VC4_BUILD_NEON instead of CFLAGS.")
v2: Fix Android build by just appending NEON_C_SOURCES when
    ARCH_ARM_HAVE_NEON.

Tested-by: Rob Herring <robh@kernel.org>