libcamera: ipa_manager: Allow IPA loading in nested subdirs

Now that we allow IPA modules to live in nested directories for the
RaspberryPi platform, it is required to allow parsing one more level
to be able to run libcamera from the source directory.

Without this patch the $(builddir)/src/ipa/rpi/vc4/ipa_rpi_vc4.so
IPA module cannot be loaded.

The issue is only present when running from the source directory
as when libcamera is installed all IPA modules are deployed to a single
$(prefix)/$(libcamera_libdir)/libamera/ location.

Fixes: 46aefed208 ("pipeline: meson: Allow nested pipeline handler directory structures")
Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Umang Jain <umang.jain@ideasonboard.com>

src/libcamera/ipa_manager.cpp

@@ -138,7 +138,7 @@ IPAManager::IPAManager()
 	std::string root = utils::libcameraBuildPath();
 	if (!root.empty()) {
 		std::string ipaBuildPath = root + "src/ipa";
-		constexpr int maxDepth = 1;
+		constexpr int maxDepth = 2;
 
 		LOG(IPAManager, Info)
 			<< "libcamera is not installed. Adding '"