x86: Rename "ignore" macro in <asm/dwarf2.h> to avoid collision

Commit 70f1bba4 ("x86: use ignore macro instead of hash comment") breaks
the 64-bit x86 build on toolchains that have CONFIG_AS_CFI undefined with:

    arch/x86/lib/csum-copy_64.S:48: Error: Macro `ignore' was already defined

because <asm/dwarf2.h> now uses the ignore macro name itself.  Fix this
by changing to __cfi_ignore in dwarf2.h.
Signed-off-by: Roland Dreier <rolandd@cisco.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/asm-x86/dwarf2.h

@@ -38,23 +38,23 @@
 
 /* Due to the structure of pre-exisiting code, don't use assembler line
    comment character # to ignore the arguments. Instead, use a dummy macro. */
-.macro ignore a=0, b=0, c=0, d=0
+.macro __cfi_ignore a=0, b=0, c=0, d=0
 .endm
 
-#define CFI_STARTPROC	ignore
-#define CFI_ENDPROC	ignore
-#define CFI_DEF_CFA	ignore
-#define CFI_DEF_CFA_REGISTER	ignore
-#define CFI_DEF_CFA_OFFSET	ignore
-#define CFI_ADJUST_CFA_OFFSET	ignore
-#define CFI_OFFSET	ignore
-#define CFI_REL_OFFSET	ignore
-#define CFI_REGISTER	ignore
-#define CFI_RESTORE	ignore
-#define CFI_REMEMBER_STATE ignore
-#define CFI_RESTORE_STATE ignore
-#define CFI_UNDEFINED ignore
-#define CFI_SIGNAL_FRAME ignore
+#define CFI_STARTPROC	__cfi_ignore
+#define CFI_ENDPROC	__cfi_ignore
+#define CFI_DEF_CFA	__cfi_ignore
+#define CFI_DEF_CFA_REGISTER	__cfi_ignore
+#define CFI_DEF_CFA_OFFSET	__cfi_ignore
+#define CFI_ADJUST_CFA_OFFSET	__cfi_ignore
+#define CFI_OFFSET	__cfi_ignore
+#define CFI_REL_OFFSET	__cfi_ignore
+#define CFI_REGISTER	__cfi_ignore
+#define CFI_RESTORE	__cfi_ignore
+#define CFI_REMEMBER_STATE __cfi_ignore
+#define CFI_RESTORE_STATE __cfi_ignore
+#define CFI_UNDEFINED __cfi_ignore
+#define CFI_SIGNAL_FRAME __cfi_ignore
 
 #endif