vulkan: Translate usage flags before passing to driver

Previously we just cast the 32bit flags and jammed them in the two
gralloc1 slots. Use the helper which does the correct translation.

(Yes, all these gralloc1isms are going away in favor of a single 64bit
flags field, but Vulkan HALs expect us to implement our side of
ANDROID_native_buffer correctly.)

(Cherry-picked from 47442912 in oc-dev)

Test: boot sailfish, run vulkan demo
Bug: 37686587
Change-Id: I806011986e8140d7f608d281798605bd9ca9a86b