Set suggestedYcbcrModel to RGB_IDENTITY for RGB formats

The YCBCR_601 model should be applied only for
YUV formats.

Bug: 131176903
Test: CtsGraphicsTestCases \
Test:     android.graphics.cts.BasicVulkanGpuTest# \
Test:     testBasicBufferImportAndRenderingExternalFormat\
Test:     [AHARDWAREBUFFER_FORMAT_R8G8B8A8_UNORM]
Change-Id: I4701464e99928d62aa6e0382daff002d2cd90003
Merged-In: I1888238a890bcbc685b63b996790d8de5f55b412
Signed-off-by: Roman Kiryanov <rkir@google.com>