nvme: split init identify into helper

The function nvme_init_ctrl_finish() (formerly nvme_init_identify()) has
grown over the period of time about ~200 lines given the size of nvme id
ctrl data structure.

Move the nvme_id_ctrl data structure related initilzation into helper
nvme_init_identify() and call it from nvme_init_ctrl_finish().

When we move the code into nvme_init_identify() change the local
variable i from int to unsigned int and remove the duplicate kfree()
after nvme_mpath_init() and jump to the label out_free if
nvme_mpath_ini() fails.

Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>