MFC r305812:

MFC r305812:

fifolog(1): invert order of calloc(3) arguments.

The second argument to calloc(3) should be the size, make it so.

While here be a little bit more cautious in fifolog_reader_open()
to protect in the unlikely event of an overflowed allocation.

git-svn-id: svn://svn.freebsd.org/base/stable/10@306910 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f