[Mellanox]Fix lpmode set when logical port is larger than 64 (#14138)

- Why I did it
In sfplpm API, the number of logical ports is hardcoded as 64. When a system contains more port than this, the SDK APIs would fail with a syslog as below

Mar 7 03:53:58.105980 r-leopard-58 ERR syncd#SDK: [MGMT_LIB.ERR] Slot [0] Module [0] has logport [0x00010069] in enabled state
Mar 7 03:53:58.105980 r-leopard-58 ERR syncd#SDK: [SDK_MGMT_LIB.ERR] Failed in __sdk_mgmt_phy_module_pwr_attr_set, error: Internal Error
Mar 7 03:53:58.106118 r-leopard-58 ERR pmon#-c: Error occurred when setting power mode for SFP module 0, slot 0, error code 1

- How I did it
Remove the hardcoded value of 64. Obtained the number of logical ports from SDK

- How to verify it
Manual testing

platform/mellanox/mlnx-platform-api/sonic_platform/sfp.py

@@ -89,7 +89,6 @@ RJ45_TYPE = "RJ45"
 REGISTER_NUM = 1
 DEVICE_ID = 1
 SWITCH_ID = 0
-SX_PORT_ATTR_ARR_SIZE = 64
 
 PMAOS_ASE = 1
 PMAOS_EE = 1
@@ -529,9 +528,13 @@ class SFP(NvidiaSFPCommon):
     @classmethod
     def get_logical_ports(cls, sdk_handle, sdk_index, slot_id):
         # Get all the ports related to the sfp, if port admin status is up, put it to list
-        port_attributes_list = new_sx_port_attributes_t_arr(SX_PORT_ATTR_ARR_SIZE)
         port_cnt_p = new_uint32_t_p()
-        uint32_t_p_assign(port_cnt_p, SX_PORT_ATTR_ARR_SIZE)
+        uint32_t_p_assign(port_cnt_p, 0)
+        rc = sx_api_port_device_get(sdk_handle, DEVICE_ID, SWITCH_ID, None,  port_cnt_p)
+
+        assert rc == SX_STATUS_SUCCESS, "sx_api_port_device_get failed, rc = %d" % rc
+        port_cnt = uint32_t_p_value(port_cnt_p)
+        port_attributes_list = new_sx_port_attributes_t_arr(port_cnt)
 
         rc = sx_api_port_device_get(sdk_handle, DEVICE_ID , SWITCH_ID, port_attributes_list,  port_cnt_p)
         assert rc == SX_STATUS_SUCCESS, "sx_api_port_device_get failed, rc = %d" % rc