x86, asm: Restore parentheses around one pushl_cfi argument

These were (intentionally) stripped by "fix CFI macro
invocations to deal with shortcomings in gas" to expose problems
with unexpected splitting of arguments by older gas also on
newer versions, but as it turns out there is at least one distro
(Ubuntu 6.06) where even not having *any* spaces in a macro
argument doesn't reliably prevent splitting into multiple
arguments.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Acked-by: Alexander van Heukelum <heukelum@fastmail.fm>
LKML-Reference: <4CC157DB020000780001E8A2@vpn.id2.novell.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>