wigig_sensing: fix driver state machine

Allow mode change from INITIALIZED to READY_STOPPED only after SPI has been
initialized. This change will prevent mode change before SPI is ready for
operation.

Change-Id: I12b52bb9c9726c2d8e615fa0c504d01c7b1e26e3
Signed-off-by: Gidon Studinski <gidons@codeaurora.org>