libcamera: MappedFrameBuffer: Use typed Flags<MapModes>

Remove the need for callers to reference PROT_READ/PROT_WRITE directly
from <sys/mman.h> by instead exposing the Read/Write mapping options as
flags from the MappedFrameBuffer class itself.

While here, introduce the <stdint.h> header which is required for the
uint8_t as part of the Plane.

Reviewed-by: Hirokazu Honda <hiroh@chromium.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

src/android/yuv/post_processor_yuv.cpp

@@ -57,7 +57,7 @@ int PostProcessorYuv::process(const FrameBuffer &source,
 	if (!isValidBuffers(source, *destination))
 		return -EINVAL;
 
-	const MappedFrameBuffer sourceMapped(&source, PROT_READ);
+	const MappedFrameBuffer sourceMapped(&source, MappedFrameBuffer::MapFlag::Read);
 	if (!sourceMapped.isValid()) {
 		LOG(YUV, Error) << "Failed to mmap camera frame buffer";
 		return -EINVAL;