staging: rtl8723bs: avoid bogus gcc warning

staging: rtl8723bs: avoid bogus gcc warning

gcc gets confused by some of the type casts and produces an
apparently senseless warning about an out-of-bound memcpy to
an unrelated array in the same structure:

drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c: In function 'rtw_cfg80211_ap_set_encryption':
cc1: error: writing 8 bytes into a region of size 0 [-Werror=stringop-overflow=]
In file included from drivers/staging/rtl8723bs/include/drv_types.h:32,
                 from drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c:10:
drivers/staging/rtl8723bs/include/rtw_security.h:98:15: note: at offset [184, 4264] into destination object 'dot11AuthAlgrthm' of size 4
   98 |         u32   dot11AuthAlgrthm;         /*  802.11 auth, could be open, shared, 8021x and authswitch */
      |               ^~~~~~~~~~~~~~~~
cc1: error: writing 8 bytes into a region of size 0 [-Werror=stringop-overflow=]
drivers/staging/rtl8723bs/include/rtw_security.h:98:15: note: at offset [264, 4344] into destination object 'dot11AuthAlgrthm' of size 4

This is a known gcc bug, and the patch here is only a workaround,
but the approach of using a temporary variable to hold a pointer
to the key also improves readability in addition to avoiding the
warning, so overall this should still help.

Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99673
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20210422152648.2891996-1-arnd@kernel.org
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>