staging: ks7010: replace IS_11BG_RATE macro with inline function

This commit replaces IS_11BG_RATE macro with is_11b_rate inline
function to improve readability.

It also fix a checkpatch script warning because a line with more
than 80 spaces.

Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>