staging: rtl8192e: simplify rtl92e_evm_db_to_percent()

Use clamp() to simplify function rtl92e_evm_db_to_percent() and reduce
object file size.

Signed-off-by: Michael Straube <straube.linux@gmail.com>
Link: https://lore.kernel.org/r/20200118195305.16685-1-straube.linux@gmail.com


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