qspi: dra7x: enable quad mode read for ti-qspi driver

This patch enables QUAD read mode for qspi to improve the
read performace while loading the binaries from qspi.

Signed-off-by: Ravi Babu <ravibabu@ti.com>
Reviewed-by: Jagannadha Sutradharudu Teki <jagannadh.teki@gmail.com>