Allow for platform specific hardware init at boot time

Reviewed By: dustin

This patch updates the existing /etc/init.d/init-arch.sh script to
also look for platform specific PRE and POST initialization handlers.

The flow of init-arch.sh is now:

1. run any platform specific PRE handler
2. run the architecture specific handler
3. run any platform specific POST handler

These changes allow for machine specific hardware initialization early
in the boot sequence.

To make use of this feature create a small shell script fragment in
the corresponding machine directory:

  machine/<vendor>/<machine_name>/rootconf/sysroot-lib-onie/init-platform

In this file implement the functions init_platform_pre_arch() and
init_platform_post_arch().

The /etc/init.d/init-arch.sh script will call these routines at boot
time.

Testing Done:

Added no-op (just echos a message) pre and post hanlders to the
kvm_x86_64 and fsl_p2020rdbpca machines.  For both cases verified the
no-op handlers execute during boot up.
kvm_x86_64:  Add platform specific hardware init script

Reviewed By: dustin

This patch exercises the platform specific PRE and POST initialization
mechanism contained in /etc/init.d/init-arch.sh

The flow of init-arch.sh is now:

1. run any platform specific PRE handler
2. run the architecture specific handler
3. run any platform specific POST handler

This patch simply adds no-op handlers that echo a message that can be
easily verified at boot time.
fsl_p2020rdbpca:  Add platform specific hardware init script

Reviewed By: dustin

This patch exercises the platform specific PRE and POST initialization
mechanism contained in /etc/init.d/init-arch.sh

The flow of init-arch.sh is now:

1. run any platform specific PRE handler
2. run the architecture specific handler
3. run any platform specific POST handler

This patch simply adds no-op handlers that echo a message that can be
easily verified at boot time.
remove /etc/init.d/rc.local feature

Reviewed By: dustin

This feature is not being used by any known machines.

The functionality of this feature is now covered by
/etc/init.d/init-arch.sh, which can accommodate two levels of platform
specific initializations.

Testing:

The changes were exercised on the kvm_x86_64 and fsl_p2020rdbpca
machines.