MLK-22654 mx7ulp: Update wdog disable sequence

MLK-22654 mx7ulp: Update wdog disable sequence

Update the mx7ulp wdog disable sequence to avoid potential reset issue
in unlock or refresh sequence. Both sequence need two words write
to wdog CNT register in 16 bus clocks window, if miss the window,
the write will cause violation in wdog and reset the chip.

Current u-boot code is using writel() function which has a DMB barrier
to order the memory access. The DMB between two words write may introduce
some delay in certain circumstance, causing the wdog reset due to 16 bus
clock window requirement.

This patch replaces writel() function by __raw_writel() to avoid such issue,
and improve to check if watchdog is already disabled or unlocked.

Signed-off-by: Ye Li <ye.li@nxp.com>
Tested-by: Breno Lima <breno.lima@nxp.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
(cherry picked from commit b8c99d5f5bcc5573d3394b68890db16b6bb5fc88)