mtd: fix the wrong timeo for panic_nand_wait()

The panic_nand_wait() expects the timeo in ms and not in jiffies.
But in nand_wait(), the timeo for panic_nand_wait() is assigned with
wrong value(jiffies + some delay). The timeo should be set like the
panic_nand_write() does.

This patch passes timeo in ms to panic_nand_wait().
And this patch also passes timeo in jiffies(converted by msecs_to_jiffies)
to time_before() which makes the code more readable.

Signed-off-by: Huang Shijie <b32955@freescale.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>