arm64: zynqmp: Set qspi tx-buswidth to 4

arm64: zynqmp: Set qspi tx-buswidth to 4

In all the ZynqMP & Versal boards dts files tx-buswidth is by default
set to 1. Due to this the framework only issues 1-1-1 write commands to
the GQSPI driver. But the GQSPI controller is capable of handling 1-4-4
write commands, so updated the tx-buswidth to 4 in ZynqMP & Versal boards
dts files. This would enable the spi-nor framework to issue 1-4-4 write
commands instead of 1-1-1. This will increase the tx data transfer rate,
as now the tx data will be transferred on four lines instead on single line.

Signed-off-by: Amit Kumar Mahapatra <amit.kumar-mahapatra@xilinx.com>