ARM: fix set_domain() macro

Avoid polluting drivers with a set_domain() macro, which interferes with
structure member names:

drivers/net/wireless/ath/ath9k/dfs_pattern_detector.c:294:33: error: macro "set_domain" passed 2 arguments, but takes just 1

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>