kernel: cut broken SPI_NOR 4K eraseblock LIMIT patch

kernel: cut broken SPI_NOR 4K eraseblock LIMIT patch

Since 4e0c54bc5bc8 ("kernel: add support for kernel 5.4"),
the spi-nor limit 4k erasesize to spi-nor chips below a configured size
patch has not functioned as intended.

For uniform erasesize SPI-NOR devices, both
nor->erase_opcode & mtd->erasesize are used in erase operations.
These are set before, and not modified by, this
CONFIG_MTD_SPI_NOR_USE_4K_SECTORS_LIMIT patch.
Thus, an SPI-NOR device with CONFIG_MTD_SPI_NOR_USE_4K_SECTORS will
always use 4k erasesize (where the device supports it).

If this patch was fixed to function as intended, there would be
cases where devices change from a 4K to a 64K erasesize.

Signed-off-by: John Thomson <git@johnthomson.fastmail.com.au>