libcamera: pixel_format: Make PixelFormat usable as a constexpr

The PixelFormat class is a lightweight wrapper around a 32-bit FourCC
and a 64-bit modifier. Make is usable as a constexpr.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

src/libcamera/pixel_format.cpp

@@ -25,25 +25,19 @@ namespace libcamera {
  */
 
 /**
+ * \fn PixelFormat::PixelFormat()
  * \brief Construct a PixelFormat with an invalid format
  *
  * PixelFormat instances constructed with the default constructor are
  * invalid, calling the isValid() function returns false.
  */
-PixelFormat::PixelFormat()
-	: fourcc_(0)
-{
-}
 
 /**
+ * \fn PixelFormat::PixelFormat(uint32_t fourcc, uint64_t modifier)
  * \brief Construct a PixelFormat from a DRM FourCC and a modifier
  * \param[in] fourcc A DRM FourCC
  * \param[in] modifier A DRM FourCC modifier
  */
-PixelFormat::PixelFormat(uint32_t fourcc, uint64_t modifier)
-	: fourcc_(fourcc), modifier_(modifier)
-{
-}
 
 /**
  * \brief Compare pixel formats for equality