meson: Remove -Wno-unused-parameter

We build libcamera with -Wno-unused-parameter and this doesn't cause
much issue internally. However, it prevents catching unused parameters
in inline functions defined in public headers. This can lead to
compilation warnings for applications compiled without
-Wno-unused-parameter.

To catch those issues, remove -Wno-unused-parameter and fix all the
related warnings with [[maybe_unused]].

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/pub_key.cpp

@@ -30,7 +30,7 @@ namespace libcamera {
  * \brief Construct a PubKey from key data
  * \param[in] key Key data encoded in DER format
  */
-PubKey::PubKey(Span<const uint8_t> key)
+PubKey::PubKey([[maybe_unused]] Span<const uint8_t> key)
 	: valid_(false)
 {
 #if HAVE_GNUTLS
@@ -73,7 +73,8 @@ PubKey::~PubKey()
  *
  * \return True if the signature is valid, false otherwise
  */
-bool PubKey::verify(Span<const uint8_t> data, Span<const uint8_t> sig) const
+bool PubKey::verify([[maybe_unused]] Span<const uint8_t> data,
+		    [[maybe_unused]] Span<const uint8_t> sig) const
 {
 #if HAVE_GNUTLS
 	const gnutls_datum_t gnuTlsData{