msm: pil-riva: Apply resets properly for restart

The Riva processor has two registers to control the cCPU resets.
An override enable register and an override value register.
Program the override enable register so that the override value
setting takes effect. Otherwise the reset may not actually be
applied.

Similarly apply a full reset to the whole processor by asserting
the top level reset (RIVA_RESET). This ensures that the registers
are reset to a known state.

Change-Id: I54370939886dc40e1cbaf45a2e2b3c3df07aeed7
CRs-Fixed: 326071
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>