soc/intel/cmn/block/pmc: Add previous sleep state strings in log

Previous sleep state showing in serial log is a magic number.
In order to let users understand its meanings directly, add
the strings to describe the modes.

TEST=build, boot the device and check the logs:
without this change, the log is like:
[DEBUG]  prev_sleep_state 0
with this change:
[DEBUG]  prev_sleep_state 0 (S0)

Change-Id: Iabe63610d3416b3b6e823746e3ccc5116fabb17d
Signed-off-by: Marx Wang <marx.wang@intel.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/78999
Reviewed-by: Subrata Banik <subratabanik@google.com>
Reviewed-by: Eric Lai <ericllai@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kapil Porwal <kapilporwal@google.com>

0 files changed, 0 insertions, 0 deletions