ARM: OMAP2+: id: cache omap_type value

There is no need to read the register with every invocation of the function,
as the value is constant. Thus, cache the value in a static variable.

Signed-off-by: Tero Kristo <t-kristo@ti.com>

arch/arm/mach-omap2/id.c

@@ -52,7 +52,10 @@ EXPORT_SYMBOL(omap_rev);
 
 int omap_type(void)
 {
-	u32 val = 0;
+	static u32 val = OMAP2_DEVICETYPE_MASK;
+
+	if (val < OMAP2_DEVICETYPE_MASK)
+		return val;
 
 	if (cpu_is_omap24xx()) {
 		val = omap_ctrl_readl(OMAP24XX_CONTROL_STATUS);