Tegra: remove circular dependency with common_def.h

This patch stops including common_def.h from platform_def.h to
fix a circular depoendency between them.

This means platform_def.h now has to define the linker macros:
* PLATFORM_LINKER_FORMAT
* PLATFORM_LINKER_ARCH

Change-Id: Icd540b1bd32fb37e0e455e9146c8b7f4b314e012
Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>