loop: Rename and merge get_size/get_loop_size to lo_calculate_size#129

blktests-ci[bot] wants to merge 2 commits intolinus-master_baselinux-blktests/linux-block:linus-master_basefrom

series/991675=>linus-masterlinux-blktests/linux-block:series/991675=>linus-masterCopy head branch name to clipboard