staging: rtl8723bs: core: Remove variable change_priority

Remove local variable change_priority, as it takes the value of the
argument priority; as both of these variables are of type u8, priority
can be modified without changing the value of its copy at the call site.
Issue found with Coccinelle.

Signed-off-by: Nishka Dasgupta <nishkadg.linux@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>