cmd: pinmux: update result of do_status

Update the result of do_status and always returns a CMD_RET_ value
(-ENOSYS was a possible result of show_pinmux).

This patch also adds pincontrol name in error messages (dev->name)
and treats correctly the status sub command when pin-controller device is
not selected.

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
3 files changed