[ARM] Handle HWCAP_VFP in VFP support code

Don't set HWCAP_VFP in the processor support file; not only does it
depend on the processor features, but it also depends on the support
code being present.  Therefore, only set it if the support code
detects that we have a VFP coprocessor attached.

Also, move the VFP handling of the coprocessor access register into
the VFP support code.

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