net: pcs: xpcs: make xpcs_get_interfaces() static

xpcs_get_interfaces() should no longer be used outside of the XPCS
code, so make it static.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/E1tTffk-007Roi-JM@rmk-PC.armlinux.org.uk


Signed-off-by: Jakub Kicinski <kuba@kernel.org>