arm64: zynqmp: Change spi-max-frequency for qspi mini

Change mini u-boot qspi spi-max-frequency to 108Mhz, make the
frequency similar to full u-boot qspi flash spi-max-frequency.

Signed-off-by: T Karthik Reddy <t.karthik.reddy@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>