HID: intel_ish-hid: tx_buf memory leak on probe/remove

ish_dev_init() allocates 512*176 bytes memory for tx_buf and stores it at
&dev->wr_free_list_head.link list on ish_probe().
But there is no deallocation of this memory in ish_remove() and in
ish_probe() error path.
So current intel-ish-ipc provides 88 KB memory leak for each
probe/release.

The patch replaces kzalloc allocation by devm_kzalloc and removes
ishtp_device *dev deallocation by kfree.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Anton Vasilyev <vasilyev@ispras.ru>
Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>