ARM: tegra: timer: don't cast __iomem pointers

Fixes a lot of:

arch/arm/mach-tegra/timer.c:75:2: warning: cast removes address space of expression
arch/arm/mach-tegra/timer.c:75:2: warning: incorrect type in argument 1 (different base types)
arch/arm/mach-tegra/timer.c:75:2:    expected void const volatile [noderef] <asn:2>*<noident>
arch/arm/mach-tegra/timer.c:75:2:    got unsigned int
arch/arm/mach-tegra/timer.c:75:2: warning: cast removes address space of expression

Signed-off-by: Olof Johansson <olof@lixom.net>
Acked-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>