staging: rtl8192e: Remove unchanged variable RegRfPsLevel

Remove unchanged variable RegRfPsLevel and equations that have always the
same result to shorten code.

Signed-off-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>
Link: https://lore.kernel.org/r/49162b0041db33c6c43c4126839baed69c76cb89.1681627603.git.philipp.g.hortmann@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>