webos.inc: Change default PACKAGE_ARCH to MACHINE_ARCH

:Release Notes:
Some components are incorrectly kept as TUNE_PKGARCH even when they
depend on something that's MACHINE_ARCH. The build layout created by mcf
doesn't support sharing binary feeds and all officially supported
MACHINE-s have different architecture, so it's easier to change the
default PACKAGE_ARCH than to fix all the components with incorrect
TUNE_PKGARCH.

:Detailed Notes:
Hopefully the design of several components will be reevaluated later and
improved to support more TUNE_PKGARCH builds, like in this example:
https://github.com/webOS-ports/meta-webos-ports/commit/7bc124393f8e59c5eb5f74e76486bb2e2f6c7b64

:Testing Performed:
Only build tested.

:QA Notes:
No functional change to image.

:Build Notes:
- Invalidates almost all shared state.
- Because this commit causes many packages to be given a different
  PACKAGE_ARCH, to avoid confusion, incremental build trees should be
  rebuilt from scratch after pulling this commit, i.e., execute:
    $ rm -rf BUILD-*
    $ ./mcf.status

:Issues Addressed:
[GF-43076] Set PACKAGE_ARCH of all compiled components to be
           MACHINE_ARCH
[GF-46352] CCC: Set the package architecture of all compiled components
           to be MACHINE

Open-webOS-DCO-1.0-Signed-off-by: Martin Jansa <martin.jansa@lge.com>
Change-Id: Ia3a74b12794d92d657c838aca8bc21fc0ed8d104
Reviewed-on: https://g2g.palm.com/3808
Reviewed-by: Build Verification
Reviewed-by: Herb Kuta <herb.kuta@lge.com>
Tested-by: Herb Kuta <herb.kuta@lge.com>
Reviewed-by: Susan Montooth <susan.montooth@lge.com>