[arm] PR target/82975: Guard against reg_renumber being NULL in arm.h

Commit missing hunk to arm.h TEST_REGNO comment.

	PR target/82975
	* config/arm/arm.h (TEST_REGNO): Adjust comment as expected in
	r255830.

From-SVN: r255853

gcc/ChangeLog

+2017-12-20  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
+
+	PR target/82975
+	* config/arm/arm.h (TEST_REGNO): Adjust comment as expected in
+	r255830.
+
 2017-12-20  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c++/83490

gcc/config/arm/arm.h

@@ -1615,10 +1615,7 @@ enum arm_auto_incmodes
 
 /* These assume that REGNO is a hard or pseudo reg number.
    They give nonzero only if REGNO is a hard reg of the suitable class
-   or a pseudo reg currently allocated to a suitable hard reg.
-   Since they use reg_renumber, they are safe only once reg_renumber
-   has been allocated, which happens in reginfo.c during register
-   allocation.  */
+   or a pseudo reg currently allocated to a suitable hard reg.  */
 #define TEST_REGNO(R, TEST, VALUE) \
   ((R TEST VALUE)	\
     || (reg_renumber && ((unsigned) reg_renumber[R] TEST VALUE)))