ARM: OMAP: Catch callers of revision information prior to it being populated

omap_rev is used to detect various SoC types, however any misuse of
the usage by invoking it earlier than it being populated will result
in invalid results. Lets flag them as early as possible to prevent
unintended side effects taking place. We get 0 if it is uninitialized
and -1 when detection is done using device tree (as the case was for
DRA7 as the case was prior to commit 06c2d368fc ("ARM: OMAP: DRA7:
Make use of omap_revision information for soc_is* calls")

Signed-off-by: Nishanth Menon <nm@ti.com>
Tested-by: Keerthy <j-keerthy@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/mach-omap1/id.c

@@ -65,6 +65,7 @@ static struct omap_id omap_ids[] __initdata = {
 
 unsigned int omap_rev(void)
 {
+	WARN_ON_ONCE(!omap_revision || omap_revision == -1);
 	return omap_revision;
 }
 EXPORT_SYMBOL(omap_rev);

arch/arm/mach-omap2/id.c

@@ -46,6 +46,7 @@ u32 omap_features;
 
 unsigned int omap_rev(void)
 {
+	WARN_ON_ONCE(!omap_revision || omap_revision == -1);
 	return omap_revision;
 }
 EXPORT_SYMBOL(omap_rev);