ARM: tegra: move resume vector define to irammap.h

irammap.h's purpose is to define the layout/usage of IRAM. As such,
TEGRA_IRAM_CODE_AREA should have been added there rather than iomap.h.
Move the define, and rename it something more descriptive.

Cc: Joseph Lo <josephl@nvidia.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>