Support HAL_PIXEL_FORMAT_BLOB in default gralloc

Test: manual, ran scrcpy with codec2's blob allocator
Change-Id: I647ed5b0e9df4920e4a02686185956aa71ee806e
diff --git a/modules/gralloc/gralloc.cpp b/modules/gralloc/gralloc.cpp
index 87bda97..f7ea01c 100644
--- a/modules/gralloc/gralloc.cpp
+++ b/modules/gralloc/gralloc.cpp
@@ -224,7 +224,11 @@
         case HAL_PIXEL_FORMAT_RAW16:
             bytesPerPixel = 2;
             break;
+        case HAL_PIXEL_FORMAT_BLOB:
+            bytesPerPixel = 1;
+            break;
         default:
+            ALOGE("gralloc_alloc bad format %d", format);
             return -EINVAL;
     }