x86: correct abort check

x86: correct abort check

I'm rather certain the missing ! was just a typo, the more with the
similar check in mind that's in the same function a few hundred lines
down (in the body of "if (vex_reg != (unsigned int) ~0)"). Of course
this can't be demonstrated by a test case - internal data structure
consistency is being checked here, and neither form of the check
triggers with any current template.

It is also not really clear to me why operand_type_equal() is being used
in the {X,Y,Z}MM register check here, rather than just testing the
respective bits: Just like Reg32|Reg64 is legal in an operand template,
I don't see why e.g. RegXMM|RegYMM wouldn't be. For example it ought to
be possible to combine

vaddpd, 3, 0x6658, None, 1, CpuAVX, Modrm|Vex|VexOpcode=0|VexVVVV=1|VexW=1|IgnoreSize|No_bSuf|No_wSuf|No_lSuf|No_sSuf|No_qSuf|No_ldSuf, { Xmmword|Unspecified|BaseIndex|Disp8|Disp16|Disp32|Disp32S|RegXMM, RegXMM, RegXMM }
vaddpd, 3, 0x6658, None, 1, CpuAVX, Modrm|Vex=2|VexOpcode=0|VexVVVV=1|VexW=1|IgnoreSize|No_bSuf|No_wSuf|No_lSuf|No_sSuf|No_qSuf|No_ldSuf, { Ymmword|Unspecified|BaseIndex|Disp8|Disp16|Disp32|Disp32S|RegYMM, RegYMM, RegYMM }

into a single template (with setting of VEX.L suitably handled elsewhere
if that's not already happening anyway).

Additionally I don't understand why this uses abort() instead of
gas_assert().

Both of these latter considerations then also apply to the
aforementioned other check in the same function.