net: stmmac: visconti: clean up code formatting

Ensure that code is wrapped prior to column 80, and shorten the
needlessly long "clk_sel_val" to just "clk_sel".

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/E1uRH2B-004UyS-Ch@rmk-PC.armlinux.org.uk


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