ath9k: fix build error with disabled debug
ath9k: fix build error with disabled debug

DFS pulse interval printing is only available
when CONFIG_ATH9K_DEBUGFS is set.

Signed-off-by: Zefir Kurtisi <7981edfe495a6661206415ce5aeb1dbd1779854d@neratec.com>
Signed-off-by: John W. Linville <2a53bac7a5d324865ef46ec4c38b2c0fba1456b4@tuxdriver.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs