Merge tag 'u-boot-imx-next-20250321' of https://gitlab.denx.de/u-boot/custodians/u-boot-imx into next

CI: https://source.denx.de/u-boot/custodians/u-boot-imx/-/pipelines/25267

- Allow the registration and enablement of the i.MX UART clocks via DM,
  without the need of manually calling init_uart_clk().
- Remove duplicated 'mmc dev ${mmcdev}' commands.
- Rework some of the RAM related Kconfig symbols for phycore_imx8mp.