[lavapipe] Close VMO handle on lvp_FreeMemory

Close mem->vmo_handle in lvp_FreeMemory and handle allocation
failures for Zircon VMO memory. Previously, lvp_FreeMemory
only freed the duplicated handle in llvmpipe but leaked the
original vmo_handle stored in lvp_device_memory, causing Sysmem
VMO handle leaks.

Test: Verified memory release without weak VMO leak warnings from
sysmem

Fixed: 541310992
Change-Id: I11b1837281bffcd1cd232cfa17d552ceea729f2c
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/mesa/+/1736749
Fuchsia-Auto-Submit: Emircan Uysaler <emircan@google.com>
Reviewed-by: Josh Gargus <jjosh@google.com>
Reviewed-by: David Gilhooley <dgilhooley@google.com>
Commit-Queue: Emircan Uysaler <emircan@google.com>