USB: pl2303: Move pl2303 vendor specific init to probe function.

Without this fix, the pl2303 usb-serial adapter would not suspend properly
unless it had been opened first.  A pl2303 type_1 chip will still break if the
system is hibernated while the RS-232 connector is powered by another system.
This was broken before, and a reset resume does not fix it.  All other suspend
and autosuspend scenarios work with ATEN pl2303 adaptors with HX and type_1 chips.

Signed-off-by: Sarah Sharp <saharabeara@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>