staging: et131x: Introduce et1310_in_phy_coma() call

In several places in the code, the pm_csr register is read and the PHY_SW_COMA bit checked.

Move this check into its own small function to make the code more readable.

Signed-off-by: Mark Einon <mark.einon@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>