remove invalid PLT calls from microblaze asm

analogous to commit 646cb9a4a04e5ed78e2dd928bf9dc6e79202f609 for sh.

src/setjmp/microblaze/setjmp.s

@@ -1,9 +1,12 @@
+.global ___setjmp
+.hidden ___setjmp
 .global __setjmp
 .global _setjmp
 .global setjmp
 .type __setjmp,@function
 .type _setjmp,@function
 .type setjmp,@function
+___setjmp:
 __setjmp:
 _setjmp:
 setjmp:

src/signal/microblaze/sigsetjmp.s

@@ -4,12 +4,13 @@
 .type __sigsetjmp,@function
 sigsetjmp:
 __sigsetjmp:
-	beqi r6, setjmp@PLT
+.hidden ___setjmp
+	beqi r6, ___setjmp
 
 	swi r15,r5,72
 	swi r19,r5,72+4+8
 
-	brlid r15,setjmp@PLT
+	brlid r15,___setjmp
 	 ori r19,r5,0
 
 	ori r6,r3,0