gpu: nvgpu: Remove Linux headers from mm_gk20a.h

Delte the Linux headers and make some modifications to get rid of the
minor compilation issues that resulted.

  - Add <linux/iommu.h> to os_linux.h
  - Delete #if 0 code that "flushed" a buffer in gr_gk20a.c
  - Delete FLUSH_CPU_DCACHE() macro
  - Move the cache flush definitions to <nvgpu/linux/vm.h>
    and include this header in sim_gk20a.c. This file will
    not be used by QNX so this should be fine.
  - Add <linux/pci_ids.h> to gp106/bios_gp106.c and
    gp106/mclk_gp106.c.
  - Move function to common/linux/dmabuf.h since it is a
    dmabuf related function and uses a struct device pointer
    as an argument.

JIRA NVGPU-30

Change-Id: I11f56b98524c7fac3efa91b4686592130e5f8a46
Signed-off-by: Alex Waterman <alexw@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/1585510
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>

drivers/gpu/nvgpu/include/nvgpu/linux/vm.h

@@ -19,6 +19,18 @@
 
 #include <nvgpu/types.h>
 
+#include <asm/cacheflush.h>
+
+/*
+ * Couple of places explicitly flush caches still. Any DMA buffer we allocate
+ * from within the GPU is writecombine and as a result does not need this but
+ * there seem to be exceptions.
+ */
+#ifdef CONFIG_ARM64
+#define outer_flush_range(a, b)
+#define __cpuc_flush_dcache_area __flush_dcache_area
+#endif
+
 struct sg_table;
 struct dma_buf;