staging:rtl8821ae: Fix sparse warnings of cast truncates bits from constant value

This patch fixes the following sparse warnings:
drivers/staging/rtl8821ae/rtl8821ae/phy.c:444:39: warning: cast truncates bits from constant value (ffffff01 becomes 1)
drivers/staging/rtl8821ae/rtl8821ae/phy.c:445:39: warning: cast truncates bits from constant value (ffffff01 becomes 1)

Signed-off-by: Himangi Saraogi <himangi774@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>