x86_64: Correct THREAD_SETMEM/THREAD_SETMEM_NC for movq [BZ #27591]

config/i386/constraints.md in GCC has

(define_constraint "e"
  "32-bit signed integer constant, or a symbolic reference known
   to fit that range (for immediate operands in sign-extending x86-64
   instructions)."
  (match_operand 0 "x86_64_immediate_operand"))

Since movq takes a signed 32-bit immediate or a register source operand,
use "er", instead of "nr"/"ir", constraint for 32-bit signed integer
constant or register on movq.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>