Fix warning shadowing result variable in the #define CHECK_ENUM

[ivan-v-kush]

Hello, in the macros CHECK_ENUM we need to remove int, i.e. not create a result var. Or change a name to another.
I think, renaming is more safe

In file included from src/libkmip/libkmip/src/kmip.c:15: src/libkmip/libkmip/src/kmip.c: In function ‘kmip_decode_name’: ../../contrib/pg_tde/src/libkmip/libkmip/include/kmip.h:1414:9: warning: declaration of ‘result’ shadows a previous local [-Wshadow=compatible-local]
     int result = kmip_check_enum_value((A)->version, (B), (C)); \
         ^~~~~~
src/libkmip/libkmip/src/kmip.c:12759:5: note: in expansion of macro ‘CHECK_ENUM’
     CHECK_ENUM(ctx, KMIP_TAG_NAME_TYPE, value->type);
     ^~~~~~~~~~
src/libkmip/libkmip/src/kmip.c:12742:9: note: shadowed declaration is here
     int result = 0;
         ^~~~~~

[lukin-oleksiy]

LGTM