spi: cadence-quadspi: Use STIG mode for all ops with small payload

OSPI controller supports all types of op variants in STIG mode,
only limitation being that the data payload should be less than
8 bytes when not using memory banks.

STIG mode is more stable for operations that send small data
payload and is more efficient than using DMA for few bytes of
memory accesses. It overcomes the limitation of minimum 4 bytes
read from flash into RAM seen in DAC mode.

Use STIG mode for all read and write operations that require
data input/output of less than 8 bytes from the flash, and thereby
support all four phases, cmd/address/dummy/data, through OSPI STIG.

Also, remove the reorder address chunk in apb_command_write since we now
setup ADDR BIT field that does the same job in a cleaner way.

Signed-off-by: Apurva Nandan <a-nandan@ti.com>
Signed-off-by: Dhruva Gole <d-gole@ti.com>
Acked-by: Jagan Teki <jagan@amarulasolutions.com>