Drivers: hv: utils: Make use of the helper macro LIST_HEAD()

Replace "struct list_head head = LIST_HEAD_INIT(head)" with
"LIST_HEAD(head)" to simplify the code.

Signed-off-by: Cai Huoqing <cai.huoqing@linux.dev>
Link: https://lore.kernel.org/r/20220209032251.37362-1-cai.huoqing@linux.dev
Signed-off-by: Wei Liu <wei.liu@kernel.org>