ARM: 7118/1: rename temp variable in read*_relaxed()

This resolves the following sparse warning from readl() and other macros,
which ends up embedding readl_relaxed() using the same variable.

arch/arm/mach-tegra/dma.c:169:8: warning: symbol '__v' shadows an earlier one
arch/arm/mach-tegra/dma.c:169:8: originally declared here

Signed-off-by: Olof Johansson <olof@lixom.net>
Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>