tools/ocaml: abi check: Cope with consecutive relevant enums

tools/ocaml: abi check: Cope with consecutive relevant enums

If the end of one enum is the `type' line for the next enum, we would
not notice it.

Fix this by reordering the code, and getting rid of the else: now if
the "we are within an enum" branch decides that it's the end of the
enum, it unsets $ei and we then immediately process the line as a "not
within an enum" line - ie as the start of the next one.

Reported-by: Paul Durrant <paul.durrant@citrix.com>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Acked-by: Christian Lindig <christian.lindig@citrix.com>