net: dsa: microchip: move interrupt handling logic from lan937x to ksz_common

To support the phy link detection through interrupt method for ksz9477
based switch, the interrupt handling routines are moved from
lan937x_main.c to ksz_common.c. The only changes made are functions
names are prefixed with ksz_ instead of lan937x_.

Signed-off-by: Arun Ramadoss <arun.ramadoss@microchip.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>