ARM: imx: romapi: Repair FlexSPI NOR boot offset

ARM: imx: romapi: Repair FlexSPI NOR boot offset

The FlexSPI NOR boot offset does not require any special handling,
the image_offset is correct in either case (0x1000 for FlexSPI NOR
and 0x8000 for SD/eMMC) and the offset of u-boot.itb from the start
of flash.bin is always 0x58000 on MX8MN/MX8MP, which matches the
CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR * 512 - 0x8000 in case
CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR=0x300, which is always the
case on MX8MN/MX8MP.

The CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR is really overloaded in
case of the MX8MN/MX8MP, but fixing that needs additional plumbing.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Fabio Estevam <festevam@denx.de>
Cc: Peng Fan <peng.fan@nxp.com>
Cc: Stefano Babic <sbabic@denx.de>