platform/x86: mlx-platform: Add UID LED for the next generation systems

Add support for UID LED for the next generation systems MQMB7xx,
MSN37xx, MSN34xx, MSN38xx.

All these systems support UID LED control through the programmable
device.
The UID LED is to be exposed to leds-mlxreg driver.

Signed-off-by: Vadim Pasternak <vadimp@mellanox.com>
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>