x86: Fixup asm-offsets duplicate

It turns out that 'stack_canary_offset' is a variable name; shadowing
that with a #define is ripe of fail when the asm-offsets.h header gets
included. Rename the thing.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

arch/x86/entry/entry_64.S

@@ -252,7 +252,7 @@ SYM_FUNC_START(__switch_to_asm)
 
 #ifdef CONFIG_STACKPROTECTOR
 	movq	TASK_stack_canary(%rsi), %rbx
-	movq	%rbx, PER_CPU_VAR(fixed_percpu_data) + stack_canary_offset
+	movq	%rbx, PER_CPU_VAR(fixed_percpu_data) + FIXED_stack_canary
 #endif
 
 	/*

arch/x86/kernel/asm-offsets_64.c

@@ -57,7 +57,7 @@ int main(void)
 	BLANK();
 
 #ifdef CONFIG_STACKPROTECTOR
-	DEFINE(stack_canary_offset, offsetof(struct fixed_percpu_data, stack_canary));
+	OFFSET(FIXED_stack_canary, fixed_percpu_data, stack_canary);
 	BLANK();
 #endif
 	return 0;