Staging: hv: storvsc: Disable clustering

Disable clustering, since the host side on Hyper-V requires that
each I/O element not exceed the page size. As part of this
cleanup, get rid of the function to merge bvecs, as the primary
reason for this function was to avoid having an element exceed
the page size.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>