xfs: fix various problems with log intent item recovery

Starting with 6.1-rc1, CONFIG_FORTIFY_SOURCE checks became smart enough
to detect memcpy() callers that copy beyond what seems to be the end of
a struct.  Unfortunately, gcc has a bug wherein it cannot reliably
compute the size of a struct containing another struct containing a flex
array at the end.  This is the case with the xfs log item format
structures, which means that -rc1 starts complaining all over the place.

Fix these problems by memcpying the struct head and the flex arrays
separately.  Although it's tempting to use the FLEX_ARRAY macros, the
structs involved are part of the ondisk log format.  Some day we're
going to want to make the ondisk log contents endian-safe, which means
that we will have to stop using memcpy entirely.

While we're at it, fix some deficiencies in the validation of recovered
log intent items -- if the size of the recovery buffer is not even large
enough to cover the flex array record count in the head, we should abort
the recovery of that item immediately.

The last patch of this series changes the EFI/EFD sizeof functions names
and behaviors to be consistent with the similarly named sizeof helpers
for other log intent items.

v2: fix more inadequate log intent done recovery validation and dump
    corrupt recovered items

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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