linux-user: Rename TARGET_QEMU_ESIGRETURN to QEMU_ESIGRETURN

This value is fully internal to qemu, and so is not a TARGET define.

Reviewed-by: Warner Losh <imp@bsdimp.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

linux-user/mips/cpu_loop.c

@@ -145,7 +145,7 @@ done_syscall:
                 env->active_tc.PC -= 4;
                 break;
             }
-            if (ret == -TARGET_QEMU_ESIGRETURN) {
+            if (ret == -QEMU_ESIGRETURN) {
                 /* Returning from a successful sigreturn syscall.
                    Avoid clobbering register state.  */
                 break;