fix hwcap access in powerpc-sf setjmp/longjmp

commit 7be59733d71ada3a32a98622507399253f1d5e48 introduced the
hwcap-based branches to support the SPE FPU, but wrongly coded them as
bitwise tests on the computed address of __hwcap, not a value loaded
from that address. replace the add with indexed load to fix it.
diff --git a/src/setjmp/powerpc/longjmp.S b/src/setjmp/powerpc/longjmp.S
index 34aecb4..611389f 100644
--- a/src/setjmp/powerpc/longjmp.S
+++ b/src/setjmp/powerpc/longjmp.S
@@ -44,7 +44,7 @@
 	.long __hwcap-.
 1:	mflr 4
 	lwz 5, 0(4)
-	add 4, 4, 5
+	lwzx 4, 4, 5
 	andis. 4, 4, 0x80
 	beq 1f
 	.long 0x11c35b01 /* evldd 14,88(3) */
diff --git a/src/setjmp/powerpc/setjmp.S b/src/setjmp/powerpc/setjmp.S
index 413e6a8..f1fcce3 100644
--- a/src/setjmp/powerpc/setjmp.S
+++ b/src/setjmp/powerpc/setjmp.S
@@ -44,7 +44,7 @@
 	.long __hwcap-.
 1:	mflr 4
 	lwz 5, 0(4)
-	add 4, 4, 5
+	lwzx 4, 4, 5
 	andis. 4, 4, 0x80
 	beq 1f
 	.long 0x11c35b21 /* evstdd 14,88(3) */