linux-imx

sparc: Improve VDSO CFLAGS.

Do not set any special register usage options, use the default which
is exactly what we should use for userspace code.

Make sure we remove the gcc plugin options from the 64-bit build.
The 32-bit cflags got it right already.

Signed-off-by: David S. Miller <davem@davemloft.net>