soundwire: Fix swr device count logic in registration

Increment swr device count before registration to
enable proper device detection in probe call, Decrement
the same count if the registration fails.

CRs-fixed: 2050725
Change-Id: If0133cbf751195542d9e1f16679cc63547b56778
Signed-off-by: Karthikeyan Mani <kmani@codeaurora.org>