x86/Intel: don't accept memory operands with J*CXZ and LOOP*

x86/Intel: don't accept memory operands with J*CXZ and LOOP*

PR gas/31887

Like for, in particular, J<cc> such should be rejected. Simplify the
respective conditional in i386_intel_operand(), leveraging that
JumpAbsolute will never occur in the first template of a mnemonic-
specific group (thus making it unnecessary to exclude that one case).

At this occasion do the same simplification later in the function as
well: The resulting two operands will uniformly be invalid for all
mnemonics other than CALL and JMP (and their AT&T counterparts, which
we've been wrongly accepting in Intel syntax) anyway.