dma-buf/heaps: Don't assert held reservation lock for dma-buf mmapping

Don't assert held dma-buf reservation lock on memory mapping of exported
buffer.

We're going to change dma-buf mmap() locking policy such that exporters
will have to handle the lock. The previous locking policy caused deadlock
problem for DRM drivers in a case of self-imported dma-bufs once these
drivers are moved to use reservation lock universally. The problem
solved by moving the lock down to exporters. This patch prepares dma-buf
heaps for the locking policy update.

Reviewed-by: Emil Velikov <[e-mail]>
Signed-off-by: Dmitry Osipenko <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/dma-buf/heaps/cma_heap.c

···
 #include <linux/dma-buf.h>
 #include <linux/dma-heap.h>
 #include <linux/dma-map-ops.h>
-#include <linux/dma-resv.h>
 #include <linux/err.h>
 #include <linux/highmem.h>
 #include <linux/io.h>
···
 static int cma_heap_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma)
 {
 	struct cma_heap_buffer *buffer = dmabuf->priv;
-
-	dma_resv_assert_held(dmabuf->resv);
 
 	if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0)
 		return -EINVAL;

drivers/dma-buf/heaps/system_heap.c

···
 #include <linux/dma-buf.h>
 #include <linux/dma-mapping.h>
 #include <linux/dma-heap.h>
-#include <linux/dma-resv.h>
 #include <linux/err.h>
 #include <linux/highmem.h>
 #include <linux/mm.h>
···
 	unsigned long addr = vma->vm_start;
 	struct sg_page_iter piter;
 	int ret;
-
-	dma_resv_assert_held(dmabuf->resv);
 
 	for_each_sgtable_page(table, &piter, vma->vm_pgoff) {
 		struct page *page = sg_page_iter_page(&piter);