udmabuf: add CONFIG_MMU dependency

There is no !CONFIG_MMU version of vmf_insert_pfn():

arm-linux-gnueabi-ld: drivers/dma-buf/udmabuf.o: in function `udmabuf_vm_fault':
udmabuf.c:(.text+0xaa): undefined reference to `vmf_insert_pfn'

Link: https://lkml.kernel.org/r/20240624063952.1572359-5-vivek.kasireddy@intel.comSigned-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Dongwon Kim <dongwon.kim@intel.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Junxiao Chang <junxiao.chang@intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

drivers/dma-buf/Kconfig

@@ -35,6 +35,7 @@ config UDMABUF
 	default n
 	depends on DMA_SHARED_BUFFER
 	depends on MEMFD_CREATE || COMPILE_TEST
+	depends on MMU
 	help
 	  A driver to let userspace turn memfd regions into dma-bufs.
 	  Qemu can use this to create host dmabufs for guest framebuffers.