twl4030-usb: cleanup debug code

Remove some debug code from twl4030-usb which 'checkpatch.pl' warned
about.  Turn some other messages into debug code; and add some debug
messages in the "write verify" paths (so we can see if they matter).
This gives about 25% codespace shrinkage.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Tony Lindgren <tony@atomide.com>