platform_data/mlxreg: Add presence register field for FAN devices

Add new field 'reg_prsnt' to the structure 'mlxreg_core_data' to
provide the number FAN drawers equpped within the system. The purpose
is to allow mapping between FAN drawers and FAN rotors (tachometer),
since FAN drawer can be eqipped with a few rotors.
Signed-off-by: Vadim Pasternak <vadimp@mellanox.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

include/linux/platform_data/mlxreg.h

@@ -75,6 +75,7 @@ struct mlxreg_hotplug_device {
  * @mask: attribute access mask;
  * @bit: attribute effective bit;
  * @capability: attribute capability register;
+ * @reg_prsnt: attribute presence register;
  * @mode: access mode;
  * @np - pointer to node platform associated with attribute;
  * @hpdev - hotplug device data;
@@ -88,6 +89,7 @@ struct mlxreg_core_data {
 	u32 mask;
 	u32 bit;
 	u32 capability;
+	u32 reg_prsnt;
 	umode_t	mode;
 	struct device_node *np;
 	struct mlxreg_hotplug_device hpdev;