Drivers: hv: vmbus: remove unused function

Fix the following clang warning:

drivers/hv/ring_buffer.c:89:1: warning: unused function
'hv_set_next_read_location' [-Wunused-function].

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/1618381282-119135-1-git-send-email-jiapeng.chong@linux.alibaba.com


Signed-off-by: Wei Liu <wei.liu@kernel.org>