MLK-21006 Driver: lpuart: Disable interrupts before request irq

MLK-21006 Driver: lpuart: Disable interrupts before request irq

Commit b311ef1d549b ("MLK-20989: Driver: lpuart: reset registers
before enable lpuart") breaks early console function, and the
commit already was reverted. The reworked patch is to fix the
issue correctly.

This patch has been tested on i.MX8QM/QXP.

change log:
V1 -> V2:
  1. Remove lock, since there is no race condition.

Suggested-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Flynn xu <flynn.xu@nxp.com>
Signed-off-by: Arulpandiyan Vadivel <arulpandiyan_vadivel@mentor.com>
Signed-off-by: Shrikant Bobade <Shrikant_Bobade@mentor.com>
(cherry picked from commit 161f0144934fe917123c79eae6a7539806d1e04e)