staging: rtl8712: Fix IEEE80211_ADDBA_PARAM_BUF_SIZE_MASK

The value in shared headers was fixed 9 years ago in commit 8d661f1e


("ieee80211: correct IEEE80211_ADDBA_PARAM_BUF_SIZE_MASK macro") and
while looking at using shared headers for other duplicated constants
I noticed this driver uses the old value.

The macros are also defined twice in this file so I am deleting the
second definition.

Signed-off-by: Pascal Terjan <pterjan@google.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20200523211247.23262-1-pterjan@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>