fs-verity: fix all kerneldoc warnings

Fix all kerneldoc warnings in fs/verity/ and include/linux/fsverity.h.
Most of these were due to missing documentation for function parameters.

Detected with:

    scripts/kernel-doc -v -none fs/verity/*.{c,h} include/linux/fsverity.h

This cleanup makes it possible to check new patches for kerneldoc
warnings without having to filter out all the existing ones.

Link: https://lore.kernel.org/r/20200511192118.71427-2-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
diff --git a/fs/verity/measure.c b/fs/verity/measure.c
index 05049b6..df409a5 100644
--- a/fs/verity/measure.c
+++ b/fs/verity/measure.c
@@ -11,6 +11,8 @@
 
 /**
  * fsverity_ioctl_measure() - get a verity file's measurement
+ * @filp: file to get measurement of
+ * @_uarg: user pointer to fsverity_digest
  *
  * Retrieve the file measurement that the kernel is enforcing for reads from a
  * verity file.  See the "FS_IOC_MEASURE_VERITY" section of