We have two prefernces determining the deco_mode (BUEHLMANN vs VPMB
vs RECREATIONAL): One for the planner (deco_mode) and one for
displaying dives (display_deco_mode). The former is set in the planner
settings while the latter is set in the preferences.
This patch clears up a confusion which of the two to use by introducing
a helper function that selects the correct variable.
Signed-off-by: Robert C. Helling <helling@atdotde.de>