More the arm64 early page tables and stack to .bss

This removes 806k from the kernel ELF file that is only needed while
the kernel is running, not in the static file.

Sponsored by:	Innovate UK

sys/arm64/arm64/locore.S

@@ -189,7 +189,7 @@ virtdone:
 .Lbss:
 	.quad	__bss_start
 .Lend:
-	.quad	_end
+	.quad	__bss_end
 
 #ifdef SMP
 /*
@@ -780,8 +780,12 @@ sctlr_clear:
 abort:
 	b abort
 
-	//.section .init_pagetable
-	.align 12 /* 4KiB aligned */
+	.align 3
+init_pt_va:
+	.quad pagetable		/* XXX: Keep page tables VA */
+
+	.section .init_pagetable, "aw", %nobits
+	.align PAGE_SHIFT
 	/*
 	 * 6 initial tables (in the following order):
 	 *           L2 for kernel (High addresses)
@@ -813,8 +817,6 @@ el2_pagetable:
 	.space	PAGE_SIZE
 
 	.globl init_pt_va
-init_pt_va:
-	.quad pagetable		/* XXX: Keep page tables VA */
 
 	.align	4
 initstack:

sys/conf/ldscript.arm64

@@ -112,8 +112,13 @@ SECTIONS
    *(.dynbss)
    *(.bss)
    *(COMMON)
+   . = ALIGN(8);
+   __bss_end = .;
+   /* A section for the initial page table, it doesn't need to be in the
+      kernel file, however unlike normal .bss entries should not be zeroed
+      out as we use it before the .bss section is cleared. */
+   *(.init_pagetable)
   }
-  . = ALIGN(8);
   _end = . ;
   PROVIDE (end = .);
   /* Stabs debugging sections.  */