ANDROID: block/keyslot-manager: fix checkpatch warning

Fix a checkpatch warning that I fixed when applying
ANDROID-dm-add-support-for-passing-through-inline-crypto-support.patch
to android12-5.4 (http://aosp/1394279

).  This gets android-mainline in
sync.

This should be folded into
ANDROID-dm-add-support-for-passing-through-inline-crypto-support.patch.

Bug: 162257830
Change-Id: I083209d174630220e3b6d148d7317600ce040a84
Signed-off-by: Eric Biggers <ebiggers@google.com>