Staging: brcm80211: s/uchar/unsigned char/

This changes the usage everywhere in the driver, and removes
the definition as it should no longer be used anywhere.

Cc: Brett Rudley <brudley@broadcom.com>
Cc: Henry Ptasinski <henryp@broadcom.com>
Cc: Nohee Ko <noheek@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>