i.MX8QXP rev C.0 requires boot container stored at offset 0KB
for eMMC, while i.MX8QXP pre C.0 requires boot container stored
at offset 32KB for eMMC.

To use one U-Boot binary to support different chip revisions,
introduce fb_mmc_get_boot_offset() to allow override the default
offset when writing to eMMC boot partitions.

This enables support for devices with non-standard boot partition
layouts, such as those requiring an offset for correct bootloader
placement.

Signed-off-by: Adrian Freihofer <adrian.freihofer@siemens.com>
Signed-off-by: Heiko Schocher <hs@nabladev.com>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@kernel.org>
Link: https://lore.kernel.org/r/20260217103604.71029-2-hs@nabladev.com
Signed-off-by: Mattijs Korpershoek <mkorpershoek@kernel.org>

Introduce fastboot block flashing functions and helpers
to be shared with the MMC implementation.

The write logic comes from the mmc implementation, while
the partition lookup is much simpler and could be extended.

For the erase logic, allmost no block drivers exposes the
erase operation, except mmc & virtio, so in order to allow
erasiong any partition a soft-erase logic has been added
to write zero-ed buffers in a loop.

Signed-off-by: Dmitrii Merkurev <dimorinny@google.com>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@kernel.org>
Tested-by: Mattijs Korpershoek <mkorpershoek@kernel.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20251121-topic-fastboot-blk-v7-1-9589d902fc91@linaro.org
Signed-off-by: Mattijs Korpershoek <mkorpershoek@kernel.org>