arm64: zynqmp: Fix usb node drive strength and slew rate

As per design, all input/rx pins should have fast slew rate and 12mA
drive strength. Rest all pins should be slow slew rate and 4mA drive
strength. Fix usb nodes as per this and remove setting of slow slew rate
for all the usb group pins.

Signed-off-by: Ashok Reddy Soma <ashok.reddy.soma@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/379071f44ceb27a0e32d74e13221640922d989d1.1684767562.git.michal.simek@amd.com