mtd: spi-nor: macronix: allow using mx25uw512 in Octal DTR mode

Set reading setting for read proto SNOR_PROTO_8_8_8_DTR with 10 dummy
cicles (will be doubled to be 20 in spi_nor_spimem_read_data) and
special read command "0xEE".

Set nor->cmd_ext_type to be SPI_NOR_EXT_REPEAT because the function
spi_nor_get_cmd_ext will check this, or else there is warning as below:

    spi-nor spi0.0: Unknown command extension type

This patch references to commit ad624dfd ("mtd: spi-nor:
micron-st: allow using MT35XU512ABA in Octal DTR mode").

Signed-off-by: Quanyang Wang <quanyang.wang@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>