Squashed 'external/devlib/' changes from 7d6ed2dd8..bdb04aa8d

bdb04aa8d ftrace: Detect tracefs mount point
8f80d8a5e shutils.in: De-hardcode tracefs location
ff599dfbb shutils.in: Simplify the dispatcher
00a5bcb37 shutils.in: Add get_fs_mount_point() function
fffa04079 target/xfer: Fix detection of files with restricted permissions

git-subtree-dir: external/devlib
git-subtree-split: bdb04aa8d00823dfab7cc2aa50283ce7da919acf