MLK-12658 imx: adjust POR_B setting on i.MX6ULL

Adjust POR_B settings on i.MX6ULL according to design
team's suggestion:

2'b00 :  always PUP100K
2'b01 :  PUP100K when PMIC_ON_REQ || SOC_NOT_FAIL
2'b10 :  always disable PUP100K
2'b11 :  PDN100K when SOC_FAIL, PUP100K when SOC_NOT_FAIL -- recommended setting

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>