arm64: dts: imx8mp-evk: correct the uart2 pinctl value

According to the IOMUXC_SW_PAD_CTL_PAD_UART2_RXD/TXD register define in
imx8mp RM, bit0 and bit3 are reserved, and the uart2 rx/tx pin should
enable the pull up, so need to set bit8 to 1. The original pinctl value
0x49 is incorrect and needs to be changed to 0x140, same as uart1 and
uart3.

Fixes: 9e847693

 ("arm64: dts: freescale: Add i.MX8MP EVK board support")
Reviewed-by: Haibo Chen <haibo.chen@nxp.com>
Signed-off-by: Sherry Sun <sherry.sun@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>