drm/xe/guc: Fix missing init value and add register order check

Fix missing initial value for last_value.
For GuC capture register definition, it is required to define 64bit
register in a pair of 2 consecutive 32bit register entries, low first,
then hi. Add code to check this order.

Changes from prior revs:
 v5:- Correct cross-line comment format
 v4:- Fix warn on condition and remove skipping
 v3:- Move break inside brace
 v2:- Correct the fix tag pointed commit
      Add examples in comments for warning
      Add 1 missing hi condition check

Fixes: ecb63364 ("drm/xe/guc: Plumb GuC-capture into dev coredump")
Signed-off-by: Zhanjun Dong <zhanjun.dong@intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241126201052.1937079-1-zhanjun.dong@intel.com