rtlwifi: Fix many compile warnings when using W=1
rtlwifi: Fix many compile warnings when using W=1

Many warnings like the following arise from a build with W=1 on the
make line:

warning: comparison of unsigned expression >= 0 is always true [-Wtype-limits]

Changing the overall debug level storage from unsigned to signed fixes these.

Signed-off-by: Larry Finger <ed0f1d78b8c21b2970494a178da4bdfa8beba2a7@lwfinger.net>
Signed-off-by: John W. Linville <2a53bac7a5d324865ef46ec4c38b2c0fba1456b4@tuxdriver.com>

KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs