arm: don't treat XScale features as part of the FPU [PR 28031]

Although the XScale and its iwMMX extensions are implemented in the
Arm co-processor space, they are not considered to be part of the FPU
specification.  In particular, they cannot be enabled or disabled via
a .fpu directive.  It's therefore incorrect to strip these properties
when a new .fpu directive is encountered.

Note that the legacy Maverick co-processor is considered to be a FPU
and it is possible to control this via the .fpu directive.

include:

	PR gas/28031
	* opcode/arm.h (FPU_ANY): Exclude XScale-related features.