staging: rtl8192u/ieee80211: Fix sparse ieee80211_debug_init/_exit not declared warning

staging: rtl8192u/ieee80211: Fix sparse ieee80211_debug_init/_exit not declared warning

A sparse warning is generated about 'ieee80211_debug_init' and
'ieee80211_debug_exit' not being declared.

  drivers/staging/rtl8192u/ieee80211/ieee80211_module.c:275:12: warning:
  symbol 'ieee80211_debug_init' was not declared. Should it be static?
  drivers/staging/rtl8192u/ieee80211/ieee80211_module.c:297:13: warning:
  symbol 'ieee80211_debug_exit' was not declared. Should it be static?

These functions are used outside of this file so using static will not
work.  The prototypes are given in r8192U_core.c but sparse nonetheless
still gives a warning.  Fix the sparse warning by moving these
prototypes from r8192U_core.c to ieee80211.h.

Signed-off-by: Jeremiah Mahler <jmmahler@gmail.com>
Cc: Joel Pelaez Jorge <joelpelaez@gmail.com>
Cc: Andrea Merello <andrea.merello@gmail.com>
Cc: "John W. Linville" <linville@tuxdriver.com>
Cc: Joe Perches <joe@perches.com>
Cc: Himangi Saraogi <himangi774@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>
Cc: Ana Rey <anarey@gmail.com>
Cc: Chaitanya Hazarey <c@24.io>
Cc: Rickard Strandqvist <rickard_strandqvist@spectrumdigital.se>
Cc: Teodora Baluta <teobaluta@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>