www/utils.c: Fix a cppcheck style issue
www/utils.c: Fix a cppcheck style issue

Fix the following

utils.c:608:15: style: Local variable 'fields' shadows outer variable [shadowVariable]
 MYSQL_FIELD *fields;
              ^
common.h:213:20: note: Shadowed declaration
struct field_names fields;
                   ^
utils.c:608:15: note: Shadow variable
 MYSQL_FIELD *fields;
              ^

by renaming the MYSQL_FIELD fields variable to mfields.

Signed-off-by: Andrew Clayton <02e0a999c50b1f88df7a8f5a04e1b76b35ea6a88@digital-domain.net>

ac000/receiptomatic