libs/utils/env: make calibration data a private attribute
libs/utils/env: make calibration data a private attribute

Signed-off-by: Patrick Bellasi <431c86f368affbc3148c4669fbd465131f7e82cb@arm.com>

JaviMerino/lisa,joelagnel/lisa,credp/lisa,mdigiorgio/lisa,ARM-software/lisa,credp/lisa,arnoldlu/lisa,credp/lisa,ARM-software/lisa,ARM-software/lisa,joelagnel/lisa,credp/lisa,bjackman/lisa,ARM-software/lisa,bjackman/lisa,arnoldlu/lisa,mdigiorgio/lisa