x86, amd_ucode: support multiple container files appended together

x86, amd_ucode: support multiple container files appended together

This patch adds support for parsing through multiple AMD container
binaries concatenated together. It is a feature already present in Linux.
Link to linux patch:
http://lkml.kernel.org/r/1370463236-2115-3-git-send-email-jacob.shin@amd.com

Other changes introduced:
 - Define HDR_SIZE's explicitly for code clarity.
 - Minor cleanup: Remove extra casts in that are used in
   install_equiv_cpu_table()

Signed-off-by: Aravind Gopalakrishnan <aravind.gopalakrishnan@amd.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>