staging:rtl8188eu: Fix sparse warning cast to restricted __le16

This patch fixes the following sparse warnings:

  CHECK   drivers/staging/rtl8188eu/hal/fw.c
drivers/staging/rtl8188eu/hal/fw.c:219:13: warning: cast to restricted __le16
drivers/staging/rtl8188eu/hal/fw.c:219:13: warning: cast to restricted __le16
drivers/staging/rtl8188eu/hal/fw.c:219:13: warning: cast to restricted __le16
drivers/staging/rtl8188eu/hal/fw.c:219:13: warning: cast to restricted __le16

by changing the signature from 'u16' to '__le16'.

Signed-off-by: Tobenna P. Igwe <ptigwe@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>