arm: Enable the VFP

Variable argument macros frequently depend on floating point
registers. Indeed we needed to enable the VFP for arm64 since its
introduction in order to use printf and the like. Somehow we
didn't need to do that for arm32 until recently when compiling
with GCC 9.

Tested-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Andrew Jones <drjones@redhat.com>