cpufreq: amd-pstate: Fix uninitialized variable in amd_pstate_cpu_boost_update()

Smatch complains that "ret" could be uninitialized:

  drivers/cpufreq/amd-pstate.c:734 amd_pstate_cpu_boost_update()
  error: uninitialized symbol 'ret'.

This seems like it probably is a real issue.  Initialize "ret" to zero to
be safe.

Fixes: c8c68c38 ("cpufreq: amd-pstate: initialize core precision boost state")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Perry Yuan <perry.yuan@amd.com>
Acked-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Link: https://lore.kernel.org/lkml/7ff53543-6c04-48a0-8d99-7dc010b93b3a@stanley.mountain/T/


Signed-off-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>