Fix the gas mixes for the Oceanic OCi.
Fix the gas mixes for the Oceanic OCi.

The Oceanic OCi supports 4 gas mixes instead of just 3, and they are
stored at a different offset.

venkateshshukla/libdivecomputer,Poltsi/libdivecomputer-vms,glance-/libdivecomputer,henrik242/libdivecomputer,josh-wambua/libdivecomputer,henrik242/libdivecomputer,venkateshshukla/libdivecomputer,glance-/libdivecomputer,josh-wambua/libdivecomputer