avr32: Use HIDDEN_JUMPTARGET() macro in bzero.S

Also, remove the hidden __memset symbol from memset.S

libc/string/avr32/bzero.S

@@ -17,7 +17,7 @@
 bzero:
        mov     r10, r11
        mov     r11, 0
-       rjmp    __memset
+       rjmp    HIDDEN_JUMPTARGET(memset)
 
        .size   bzero, . - bzero
 

libc/string/avr32/memset.S

@@ -16,13 +16,8 @@
        .global memset
        .type   memset, @function
 
-       .global __memset
-       .hidden __memset
-       .type   __memset, @function
-
        .align  1
 memset:
-__memset:
        cp.w    n, 32
        mov     r9, s
        brge    .Llarge_memset