wlcore: add quirk to disable ELP

ELP is a very complicated process in the firmware.  Due to its
complexity, in some early firmware revisions, the ELP feature is
disabled.  To support this cases, this patch adds a quirk that
disables ELP mode.

When ELP is not supported, do not attempt to enter ELP when requested by
the driver.

Signed-off-by: Luciano Coelho <coelho@ti.com>
Signed-off-by: Arik Nemtsov <arik@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>