fscrypt, pfk, ice: cover ICE-related data structures in CONFIG_PFK

This patch makes CONFIG_PFK cover all the per-file key structures.
Otherwise, for example, f2fs will set DUN, resulting in IO fragmentation,
even if PFK is not set.

Bug: 68721442
Change-Id: I93808db0b00feae53888fd9ae6c91fc2727ffca9
Signed-off-by: Jaegeuk Kim <jaegeuk@google.com>
Signed-off-by: Neeraj Soni <neersoni@codeaurora.org>