ACPICA: String conversions: Cleanup/format comments. No functional changes

ACPICA commit 33e38cd2406709b13fa0a7821e588505b3771163

Cleanup some of the language used in the large comments, especially
the ones that reference the rules in the ACPI spec.
Fixed some typos.

Link: https://github.com/acpica/acpica/commit/33e38cd24067


Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>