media: platform: allegro-dvt: Fix possible memory leak in allocate_buffers_internal()

The buffer in the loop should be released under the exception path,
otherwise there may be a memory leak here.

To mitigate this, free the buffer when allegro_alloc_buffer fails.

Fixes: f20387df ("media: allegro: add Allegro DVT video IP core driver")
Cc: <stable@vger.kernel.org>
Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>