net: sfp: improve poll interval handling

The poll interval is a fixed value, so we don't need a static variable
for it. The change also allows to use standard macro
module_platform_driver, avoiding some boilerplate code.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Link: https://patch.msgid.link/b8079f96-6865-431c-a908-a0b9e9bd5379@gmail.com


Signed-off-by: Paolo Abeni <pabeni@redhat.com>