rtc: tegra: remove set but unused variable

Fix the following warning:
drivers/rtc/rtc-tegra.c: In function ‘tegra_rtc_read_time’:
drivers/rtc/rtc-tegra.c:106:11: warning: variable ‘msec’ set but not used [-Wunused-but-set-variable]

Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Jonathan Hunter <jonathanh@nvidia.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20191122102212.400158-8-alexandre.belloni@bootlin.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/rtc-tegra.c

@@ -103,7 +103,7 @@ static int tegra_rtc_read_time(struct device *dev, struct rtc_time *tm)
 {
 	struct tegra_rtc_info *info = dev_get_drvdata(dev);
 	unsigned long flags;
-	u32 sec, msec;
+	u32 sec;
 
 	/*
 	 * RTC hardware copies seconds to shadow seconds when a read of
@@ -111,7 +111,7 @@ static int tegra_rtc_read_time(struct device *dev, struct rtc_time *tm)
 	 */
 	spin_lock_irqsave(&info->lock, flags);
 
-	msec = readl(info->base + TEGRA_RTC_REG_MILLI_SECONDS);
+	readl(info->base + TEGRA_RTC_REG_MILLI_SECONDS);
 	sec = readl(info->base + TEGRA_RTC_REG_SHADOW_SECONDS);
 
 	spin_unlock_irqrestore(&info->lock, flags);