cam: sdl: Use uint32_t in place of SDL_PixelFormatEnum

The SDL_PixelFormatEnum type has been introduced in libsdl by
1a4c0d4e17e6 ("Fixed bug 4377 - SDL_PIXELFORMAT enum is anonymous, which
prevents its use in a templated function") which is only available after
release 2.0.10 of the library.

Debian 10 ships libsdl at version 2.0.9 and building cam with sdl
support there fails with error:
./src/cam/sdl_texture.h:27:8: error: ‘SDL_PixelFormatEnum’ does not name
a type; did you mean ‘SDL_PixelFormat’?

Fix that by using the base type uint32_t in place of
SDL_PixelFormatEnum.

Reported-by: https://buildbot.libcamera.org/#/builders/6/builds/355
Fixes: 11554a259f ("cam: sdl_sink: Add SDL sink with initial YUYV support")
Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Umang Jain <umang.jain@ideasonboard.com>
Reviewed-by: Eric Curtin <ecurtin@redhat.com>

src/cam/sdl_texture.cpp

@@ -9,7 +9,7 @@
 
 #include <iostream>
 
-SDLTexture::SDLTexture(const SDL_Rect &rect, SDL_PixelFormatEnum pixelFormat,
+SDLTexture::SDLTexture(const SDL_Rect &rect, uint32_t pixelFormat,
 		       const int pitch)
 	: ptr_(nullptr), rect_(rect), pixelFormat_(pixelFormat), pitch_(pitch)
 {