[ARM] 3472/1: Use the D variants of FLDMIA/FSTMIA on ARMv6

Patch from Catalin Marinas

The X variants are deprecated starting with ARMv6. Using the D variants,
the fpmx_state in vfp_hard_struct is no longer needed.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>