iwlegacy: avoid -Wempty-body warning

There are a couple of warnings in this driver when building with W=1:

drivers/net/wireless/intel/iwlegacy/common.c: In function 'il_power_set_mode':
drivers/net/wireless/intel/iwlegacy/common.c:1195:60: error: suggest braces around empty body in an 'if' statement [-Werror=empty-body]
 1195 |                                 il->chain_noise_data.state);
      |                                                            ^
drivers/net/wireless/intel/iwlegacy/common.c: In function 'il_do_scan_abort':
drivers/net/wireless/intel/iwlegacy/common.c:1343:57: error: suggest braces around empty body in an 'else' statement [-Werror=empty-body]

Change the empty debug macros to no_printk(), which avoids the
warnings and adds useful format string checks.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Stanislaw Gruszka <stf_xl@wp.pl>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20210322104343.948660-3-arnd@kernel.org