phal: set pdbg environment variable

pdbg needs PDBG_DTB environment variable initialisation
prior to pdbg init to set correct device tree back-end.

Tested: verified  normal boot without systemd global variable set.

Signed-off-by: Jayanth Othayoth <ojayanth@in.ibm.com>
Change-Id: I7ac70cbb1966edcb85db0a862781149a0bc0f492
1 file changed