x86/hyperv: Add common print prefix "Hyper-V" in hv_init

Add "#define pr_fmt()" in hv_init.c to use "Hyper-V:" as common
print prefix for all pr_*() statements in this file.

Remove the "Hyper-V:" already prefixed in couple of prints.

Signed-off-by: Saurabh Sengar <ssengar@linux.microsoft.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Link: https://lore.kernel.org/r/1695123361-8877-1-git-send-email-ssengar@linux.microsoft.com