serial: imx: clean up imx_poll_put_char()

serial: imx: clean up imx_poll_put_char()

imx_put_poll_char() has been simplified to remove the code to disable
interrupts. The present code can corrupt register state when re-entered
from FIQ handler.

Switch to _relaxed() MMIO functions (which are safe for polled I/O and
needed to avoid taking spin locks).

Signed-off-by: Daniel Thompson <[email protected]>
Signed-off-by: Dirk Behme <[email protected]>
Cc: Jiri Slaby <[email protected]>
Cc: Huang Shijie <[email protected]>
Cc: [email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>