memstick: allow "set_param" method to return an error code

Some controllers (Jmicron, for instance) can report temporal failure
condition during power-on.  It is desirable to account for this using a
return value of "set_param" device method.  The return value can also be
handy to distinguish between supported and unsupported device parameters
in run time.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Alex Dubov <oakad@yahoo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>