Add default maxBufferCount in GraphicBufferProducer

Some modules that inherit and use IGraphicBufferProducer
don't set maxBufferCount. As a result, the maxBufferCount value
that has been queried in libvulkan is 0,
and the creation of swapchain fails.

Therefore, the default value (64) is set to maxBufferCount.

Test: build, Mcts
Bug: 376142095

Change-Id: Ie5c5f747ecd6c15ffae80cc32b9f5a90b1a44df3
Signed-off-by: sm1021.shin <sm1021.shin@samsung.com>

Author: sm1021.shin

libs/gui/include/gui/IGraphicBufferProducer.h

@@ -403,7 +403,7 @@ class IGraphicBufferProducer : public RefBase {
         uint64_t nextFrameNumber{0};
         FrameEventHistoryDelta frameTimestamps;
         bool bufferReplaced{false};
-        int maxBufferCount{0};
+        int maxBufferCount{BufferQueueDefs::NUM_BUFFER_SLOTS};
         status_t result{NO_ERROR};
     };