Drivers: hv: balloon: Remove dependencies on guest page size

Hyper-V assumes page size to be 4K. This might not be the case for
ARM64 architecture. Hence use hyper-v specific page size and page
shift definitions to avoid conflicts between different host and guest
page sizes on ARM64.

Also, remove some old and incorrect comments and redefine ballooning
granularities to handle larger page sizes correctly.

Signed-off-by: Himadri Pandya <himadri18.07@gmail.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>