ssbi: Move ssbi struct to header file

Add support to use SSBI1 and SSBI2 from a single driver.

Change-Id: I673adc3633851dd76d2deb5ffbb4182ece578029
Acked-by: Edward Rodrigues <erodrigu@qti.qualcomm.com>
Signed-off-by: Rohit Vaswani <rvaswani@codeaurora.org>