staging: rtl8723au: core: remove redundant endianness conversion

Source and destination have the same little-endian annotation: this
patch removes incorrect byte-swap on non-LE cpus.

This addresses the following sparse warning:
drivers/staging/rtl8723au/core/rtw_mlme_ext.c:3911:56: warning: incorrect type in argument 1 (different base types)
drivers/staging/rtl8723au/core/rtw_mlme_ext.c:3911:56:    expected unsigned short [unsigned] [usertype] val
drivers/staging/rtl8723au/core/rtw_mlme_ext.c:3911:56:    got restricted __le16 [usertype] BA_timeout_value

Signed-off-by: David Decotigny <ddecotig@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>