Add support for tachometer speed register for the next generation systems MQMB7xx, MSN37xx, MSN34xx, MSN38xx. All these systems support tachometer speed capability register. This register is to be provided mlxreg-fan driver. Signed-off-by: Vadim Pasternak <vadimp@mellanox.com> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>