arm64 libc: hide .cerror, .curbrk, .minbrk for WITHOUT_SYMVER

When symver is in use these are hidden because they're not listed in
the Symbol.map. Add an explicit .hidden so they are also hidden in the
WITHOUT_SYMVER case.

Reviewed by:	andrew
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D5775

lib/libc/aarch64/sys/brk.S

@@ -37,6 +37,7 @@ __FBSDID("$FreeBSD$");
 	.data
 	.align	3
 	.globl	_C_LABEL(minbrk)
+	.hidden	_C_LABEL(minbrk)
 	.type	_C_LABEL(minbrk),#object
 _C_LABEL(minbrk):
 	.quad	_C_LABEL(_end)

lib/libc/aarch64/sys/cerror.S

@@ -29,6 +29,7 @@
 __FBSDID("$FreeBSD$");
 
 ENTRY(cerror)
+	.hidden	cerror
 	sub	sp, sp, #16
 	stp	x0, lr, [sp]
 	bl	_C_LABEL(__error)

lib/libc/aarch64/sys/sbrk.S

@@ -37,6 +37,7 @@ __FBSDID("$FreeBSD$");
 	.data
 	.align	3
 	.global	_C_LABEL(curbrk)
+	.hidden	_C_LABEL(curbrk)
 	.type	_C_LABEL(curbrk),#object
 _C_LABEL(curbrk):
 	.quad	_C_LABEL(_end)