staging: rtl8723au: rtw_sta_mgt: change rtw_alloc_stainfo23a to use gfp_t instead if int

This should fix a few sparse warnings like the following:

  CHECK   drivers/staging/rtl8723au/core/rtw_ap.c
drivers/staging/rtl8723au/core/rtw_ap.c:1054:45: warning: incorrect type in argument 3 (different base types)
drivers/staging/rtl8723au/core/rtw_ap.c:1054:45:    expected int [signed] gfp
drivers/staging/rtl8723au/core/rtw_ap.c:1054:45:    got restricted gfp_t

Signed-off-by: Karim Raslan <karim.allah.ahmed@gmail.com>
Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>