x86/asm: Remove unused L3_PAGE_OFFSET

L3_PAGE_OFFSET was introduced in commit a6523748 (paravirt/x86, 64-bit: move
__PAGE_OFFSET to leave a space for hypervisor), but has no users.
Signed-off-by: Alexander Kuleshov <kuleshovmail@gmail.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Link: http://lkml.kernel.org/r/1453810881-30622-1-git-send-email-kuleshovmail@gmail.comSigned-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/head_64.S

@@ -38,7 +38,6 @@
 #define pud_index(x)	(((x) >> PUD_SHIFT) & (PTRS_PER_PUD-1))
 
 L4_PAGE_OFFSET = pgd_index(__PAGE_OFFSET)
-L3_PAGE_OFFSET = pud_index(__PAGE_OFFSET)
 L4_START_KERNEL = pgd_index(__START_KERNEL_map)
 L3_START_KERNEL = pud_index(__START_KERNEL_map)