staging/easycap: reduce code nesting in easycap_sound.c

Reshuffle error handling to reduce indentation nesting
This reduce number of lines exceeding 80 characters
from 41 to 15

use:
if (error)
	(return, goto, continue)
CODE

instead of:

if (good)
	<CODE>
else
	<EXCEPTION HANDLING>

Cc: Dan Carpenter <error27@gmail.com>
Cc: Mike Thomas <rmthomas@sciolus.org>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>