drm_hwcomposer: fix BufferInfoImagination build
Commit e9fbd8d626a2 ("drm_hwcomposer: Set return type to std::optional for
BufferInfoGetters") changed the BufferInfo variable name, but missed the case
defined under HAL_PIXEL_FORMAT_BGRX_8888. This results in build failures.
This patch fixes the build issue by completing the variable renaming.
Fixes: e9fbd8d626a2 ("drm_hwcomposer: Set return type to std::optional for BufferInfoGetters")
Signed-off-by: Andrii Chepurnyi <andrii_chepurnyi@epam.com>