spi: mtd: Use split reads if multi-die flag is set

spi: mtd: Use split reads if multi-die flag is set

Some flash devices have multiple dies in it & has die cross over
issue. When SPI_NOR_MULTI_DIE flag is set in flash id table use
it to enable split reads to avoid above issue. Define SPI_NOR_MULTI_DIE
new flag to flash id flags. Remove SPI_FLASH_SPLIT_READ config and
related code from the zynq and zynqmp qspi drivers as it is redundant.

Signed-off-by: T Karthik Reddy <t.karthik.reddy@xilinx.com>
Signed-off-by: Ashok Reddy Soma <ashok.reddy.soma@xilinx.com>