ide-tape: remove atomic test/set macros for packet commands

Removing the atomic tests for pc's is unobjectionable. Since this driver will
probably go to /dev/null soon, the atomic tests for tape->flags are left in
place for there are some situations where they're needed (chrdev DSC handling,
low level pipeline operation and so on). While at it, rename all test/set flag
bit defines explicitly to *_FLAG_* for clarity.

Signed-off-by: Borislav Petkov <petkovbb@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>