x86/asm: Fix UNWIND_HINT_REGS macro for older binutils

Apparently the binutils 2.20 assembler can't handle the '&&' operator in
the UNWIND_HINT_REGS macro.  Rearrange the macro to do without it.

This fixes the following error:

  arch/x86/entry/entry_64.S: Assembler messages:
  arch/x86/entry/entry_64.S:521: Error: non-constant expression in ".if" statement
  arch/x86/entry/entry_64.S:521: Error: non-constant expression in ".if" statement
  arch/x86/entry/entry_64.S:521: Error: non-constant expression in ".if" statement
  arch/x86/entry/entry_64.S:521: Error: non-constant expression in ".if" statement
  arch/x86/entry/entry_64.S:521: Error: non-constant expression in ".if" statement
  arch/x86/entry/entry_64.S:521: Error: non-constant expression in ".if" statement
  arch/x86/entry/entry_64.S:521: Error: non-constant expression in ".if" statement
  arch/x86/entry/entry_64.S:521: Error: non-constant expression in ".if" statement
  arch/x86/entry/entry_64.S:521: Error: non-constant expression in ".if" statement

Reported-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 39358a033b2e ("objtool, x86: Add facility for asm code to provide unwind hints")
Link: http://lkml.kernel.org/r/e2ad97c1ae49a484644b4aaa4dd3faa4d6d969b2.1502116651.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/include/asm/unwind_hints.h

@@ -44,10 +44,12 @@
 .endm
 
 .macro UNWIND_HINT_REGS base=%rsp offset=0 indirect=0 extra=1 iret=0
-	.if \base == %rsp && \indirect
-		.set sp_reg, ORC_REG_SP_INDIRECT
-	.elseif \base == %rsp
-		.set sp_reg, ORC_REG_SP
+	.if \base == %rsp
+		.if \indirect
+			.set sp_reg, ORC_REG_SP_INDIRECT
+		.else
+			.set sp_reg, ORC_REG_SP
+		.endif
 	.elseif \base == %rbp
 		.set sp_reg, ORC_REG_BP
 	.elseif \base == %rdi