arm64: a37xx: pinctrl: Improve description for pinmux command

In more cases group name consist of function name followed by function
number. So if function name is just prefix of group name, show group name.

So in 'pinmux status -a' command output would be visible also extended
function number, which is useful for debugging.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Stefan Roese <sr@denx.de>