powerpc/entry: Fix an #if which should be an #ifdef in entry_32.S

Fixes: 12c3f1fd ("powerpc/32s: get rid of CPU_FTR_601 feature")
Cc: stable@vger.kernel.org # v5.4+
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/a99fc0ad65b87a1ba51cfa3e0e9034ee294c3e07.1582034961.git.christophe.leroy@c-s.fr

arch/powerpc/kernel/entry_32.S

@@ -783,7 +783,7 @@ fast_exception_return:
 1:	lis	r3,exc_exit_restart_end@ha
 	addi	r3,r3,exc_exit_restart_end@l
 	cmplw	r12,r3
-#if CONFIG_PPC_BOOK3S_601
+#ifdef CONFIG_PPC_BOOK3S_601
 	bge	2b
 #else
 	bge	3f
@@ -791,7 +791,7 @@ fast_exception_return:
 	lis	r4,exc_exit_restart@ha
 	addi	r4,r4,exc_exit_restart@l
 	cmplw	r12,r4
-#if CONFIG_PPC_BOOK3S_601
+#ifdef CONFIG_PPC_BOOK3S_601
 	blt	2b
 #else
 	blt	3f