hal: Fix race condition in parsing platform info xml

Section is a global variable in platform info parsing functions and
both platform and acdb_extn will call into platform_info_init(). As
a result, there's a race condition happening.

Adding mutex lock to ensure file parsing in atomic.

CRs-Fixed: 2521912
Change-Id: Ic323618057ca2dc21ff60d280cb7a6de3a3271ed