x86, asm: Fix binutils 2.15 build failure

Add parentheses around one pushl_cfi argument.

Commit df5d187 "x86: Use {push,pop}{l,q}_cfi in more places"
caused GNU assembler 2.15 (Debian Sarge) to fail. It is still
failing as of commit 07bd851 "x86, asm: Restore parentheses
around one pushl_cfi argument". This patch solves build failure
with GNU assembler 2.15.

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: Jan Beulich <jbeulich@novell.com>
Cc: heukelum@fastmail.fm
Cc: hpa@linux.intel.com
LKML-Reference: <201011160445.oAG4jGif079860@www262.sakura.ne.jp>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/entry_32.S

@@ -395,7 +395,7 @@ sysenter_past_esp:
 	 * A tiny bit of offset fixup is necessary - 4*4 means the 4 words
 	 * pushed above; +8 corresponds to copy_thread's esp0 setting.
 	 */
-	pushl_cfi (TI_sysenter_return-THREAD_SIZE_asm+8+4*4)(%esp)
+	pushl_cfi ((TI_sysenter_return)-THREAD_SIZE_asm+8+4*4)(%esp)
 	CFI_REL_OFFSET eip, 0
 
 	pushl_cfi %eax