staging: rtl8712: Fixes for simple typos in C comments

Fixes for simple typos in C comments.
Found using checkpatch.pl.

Signed-off-by: R Veera Kumar <vkor@vkten.in>
Link: https://lore.kernel.org/r/20200312091042.GA4246@tulip.local


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>