ibmpex: add endian annotation to extract_data() helper

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Cc: "Darrick J. Wong" <djwong@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>