libpam: Add pam package to DISTRO_FEATURES variable

Fix the libpam compiling warning caused by the missing of pam package
from the DISTRO_FEATURE variable:
WARNING: Building libpam but 'pam' isn't in DISTRO_FEATURES, PAM won't
work correctly

Signed-off-by: Daniel Dragomir <daniel.dragomir@windriver.com>
linux-yocto: Reorganize and update LSI PUBLIC repos

- Reorganize linux-yocto inc files for GitHub public repos by setting
  LSI_KERNEL_TAG and LINUX_VERSION variable in specific lsi-public*.inc
- Update LSI_KERNEL_TAG, LINUX_VERSION and SRCREV to build the latest
  released kernels from the public 3.10 repository - tag 8.8.1.33.

Signed-off-by: Daniel Dragomir <daniel.dragomir@windriver.com>
linux-yocto: Remove not used/supported targets

As long as some targets are not supported anymore, do not create
dtb and fit images:
- axm-ve-tc1 and axm-ve-tc2 were for the arm development boards, and are
  no longer used.
- We don't need both ACP344xV2 and acp344x.  V1 of the 3448 is no longer
  supported. Remove ACP344xV2 and use acp344x.

Signed-off-by: Daniel Dragomir <daniel.dragomir@windriver.com>
README: Update informations about meta-lsi layer

- Update Supported MACHINES and Reference Boards chapter
- Add informations about building the layer and other usefull and
  required infos

Signed-off-by: Daniel Dragomir <daniel.dragomir@windriver.com>