staging: rtl8712: fix multiline derefernce warnings

This patch fixes remaining checkpatch warnings
in rtl871x_xmit.c:

WARNING: Avoid multiple line dereference - prefer 'psecuritypriv->PrivacyKeyIndex'
636: FILE: drivers/staging//rtl8712/rtl871x_xmit.c:636:
+					      (u8)psecuritypriv->
+					      PrivacyKeyIndex);

WARNING: Avoid multiple line dereference - prefer 'psecuritypriv->XGrpKeyid'
643: FILE: drivers/staging//rtl8712/rtl871x_xmit.c:643:
+						   (u8)psecuritypriv->
+						   XGrpKeyid);

WARNING: Avoid multiple line dereference - prefer 'psecuritypriv->XGrpKeyid'
652: FILE: drivers/staging//rtl8712/rtl871x_xmit.c:652:
+						   (u8)psecuritypriv->
+						   XGrpKeyid);

Signed-off-by: Aiman Najjar <aiman.najjar@hurranet.com>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/98805a72b92e9bbf933e05b827d27944663b7bc1.1585508171.git.aiman.najjar@hurranet.com


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