build: always prefix section names with `.`

Some of our specialized sections are not prefixed with the conventional
period. The compiler uses input section names to derive certain other
section names (e.g. `.rela.text`, `.relacpu_ops`), and these can be
difficult to select in linker scripts when there is a lack of a
delimiter.

This change introduces the period prefix to all specialized section
names.

BREAKING-CHANGE: All input and output linker section names have been
 prefixed with the period character, e.g. `cpu_ops` -> `.cpu_ops`.

Change-Id: I51c13c5266d5975fbd944ef4961328e72f82fc1c
Signed-off-by: Chris Kay <chris.kay@arm.com>
diff --git a/lib/pmf/pmf_main.c b/lib/pmf/pmf_main.c
index 131a055..ce2f0d9 100644
--- a/lib/pmf/pmf_main.c
+++ b/lib/pmf/pmf_main.c
@@ -17,7 +17,7 @@
 
 /*******************************************************************************
  * The 'pmf_svc_descs' array holds the PMF service descriptors exported by
- * services by placing them in the 'pmf_svc_descs' linker section.
+ * services by placing them in the '.pmf_svc_descs' linker section.
  * The 'pmf_svc_descs_indices' array holds the index of a descriptor in the
  * 'pmf_svc_descs' array. The TIF[15:10] bits in the time-stamp id are used
  * to get an index into the 'pmf_svc_descs_indices' array. This gives the