Suunto EON Steel: initialize the tank 'gasmix' index

The gasmix query interface considers cylinders and gas mixes independent
things, so the tank data structure has a pointer to the gasmix index.

But the EON Steel treats cylinders as just having a gasmix (and so does
subsurface, for that matter), so the gasmix index for the tank is just
the same as the tank index.

But we never filled it in, so you'd always see a "gas index" of zero,
and subsurface would end up warning each time about how the gasmix index
doesn't match the cylinder index (but because subsurface actually agreed
with EON Steel, it worked despite the warning).

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

src/suunto_eonsteel_parser.c

@@ -1007,6 +1007,7 @@ suunto_eonsteel_parser_get_field(dc_parser_t *parser, dc_field_type_t type, unsi
 		 * that metric is (at least so far) always whole liters
 		 */
 		tank->volume = eon->cache.tanksize[flags];
+		tank->gasmix = flags;
 
 		/*
 		 * The pressure reported is NOT the pressure the user enters.