[media] mb86a20s: don't use state before initializing it

As reported by Feng's kbuild test:
	From: kbuild test robot <fengguang.wu@intel.com>
	Subject: drivers/media/dvb-frontends/mb86a20s.c:706 mb86a20s_attach() error: potential null dereference 'state'.  (kzalloc returns null)
	Date: Wed, 23 Jan 2013 19:30:43 +0800

	commit: f66d81b5 [media] mb86a20s: convert it to use dev_info/dev_err/dev_dbg

	drivers/media/dvb-frontends/mb86a20s.c:706 mb86a20s_attach() error: potential null dereference 'state'.  (kzalloc returns null)
	drivers/media/dvb-frontends/mb86a20s.c:706 mb86a20s_attach() error: we previously assumed 'state' could be null (see line 705)

As, at mb86a20s_attach(), we have an i2c pointer, use it for all printk
messages there, instead of state->i2c.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>