Fix page table bits and allow to build with ARCH=um

Different architectures may have the PAGE* macros defined - they are not exclusive to x86. Here the defines are used to create the GPU-specific defines. Since Intel GPUs originated on x86/x86-64, using system memory, it's natural they use the same bit definition. However it's wrong to assume the page tables would have different bit definition depending on the architecture: they depend on the GPU. For integrated, they will just match CPU.

Example can be seen with git grep "define *_PAGE_PRESENT" - each arch has its own defines, but the Intel's GPU should follow the same bit definition as x86.

Signed-off-by: Lucas De Marchi lucas.demarchi@intel.com