clocksource: dbx500-prcmu: use relaxed readl variant

Modify clksrc_dbx500_prcmu_read to replace readl() with readl_relaxed().
This speeds up calls to the function by about 40%.
Signed-off-by: NRabin Vincent <rabin.vincent@stericsson.com>
Acked-by: NLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: NFabio Baltieri <fabio.baltieri@linaro.org>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>

drivers/clocksource/clksrc-dbx500-prcmu.c

@@ -30,15 +30,14 @@
 
 static void __iomem *clksrc_dbx500_timer_base;
 
-static cycle_t clksrc_dbx500_prcmu_read(struct clocksource *cs)
+static cycle_t notrace clksrc_dbx500_prcmu_read(struct clocksource *cs)
 {
+	void __iomem *base = clksrc_dbx500_timer_base;
 	u32 count, count2;
 
 	do {
-		count = readl(clksrc_dbx500_timer_base +
-			      PRCMU_TIMER_DOWNCOUNT);
-		count2 = readl(clksrc_dbx500_timer_base +
-			       PRCMU_TIMER_DOWNCOUNT);
+		count = readl_relaxed(base + PRCMU_TIMER_DOWNCOUNT);
+		count2 = readl_relaxed(base + PRCMU_TIMER_DOWNCOUNT);
 	} while (count2 != count);
 
 	/* Negate because the timer is a decrementing counter */