staging: rtl8723au: fix sparse warning

drivers/staging/rtl8723au/hal/rtl8723a_hal_init.c:747:1: warning: symbol
'rtl8723a_EfusePgPacketRead' was not declared. Should it be static?

Function 'rtl8723a_EfusePgPacketRead' seems to be unused in current
staging code.

Before, it was available as 'static s32 Hal_EfusePgPacketRead',
but code that was using it removed, in the same commit as rename and
signature change to 'bool rtl8723a_EfusePgPacketRead' has taken place.

Signed-off-by: Aleh Suprunovich <br@ahlamon.org>
Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>