bfin: fix fp reference in _JMPBUF_UNWINDS

We want to access the frame pointer, so do so directly rather than
"overflowing" the pregs array and ending up at the fp member.

This fixes the Blackfin build warnings:
libpthread/linuxthreads.old/ptlongjmp.c: In function 'pthread_cleanup_upto':
libpthread/linuxthreads.old/ptlongjmp.c:35: warning: array subscript is above array bounds
libpthread/linuxthreads.old/ptlongjmp.c:56: warning: array subscript is above array bounds

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

libc/sysdeps/linux/bfin/bits/setjmp.h

@@ -52,6 +52,6 @@ typedef struct
 /* Test if longjmp to JMPBUF would unwind the frame
    containing a local variable at ADDRESS.  */
 #define _JMPBUF_UNWINDS(jmpbuf, address) \
-  ((void *) (address) < (void *) (jmpbuf)->__pregs[6])
+  ((void *) (address) < (void *) (jmpbuf)->fp)
 
 #endif	/* bits/setjmp.h */