sepolicy: add missing labels for same process HALs.

Some of the same process HAL labeling was missing from Marlin.
These are identified by tracking library dependencies.

Bug: 37084733
Test: Build and boot sailfish. The change allows the labelled libraries
      to be opened by any domain. So, the boot test is sufficient.

Change-Id: Id55e834d6863ca644f912efdd690fccb71d3eaf3
Signed-off-by: Sandeep Patil <sspatil@google.com>

vendor/file_contexts

@@ -39,6 +39,7 @@
 #
 /(vendor|system/vendor)/lib(64)?/hw/android\.hardware\.graphics\.mapper@2\.0-impl\.so u:object_r:same_process_hal_file:s0
 /(vendor|system/vendor)/lib(64)?/hw/android\.hardware\.renderscript@1\.0-impl\.so     u:object_r:same_process_hal_file:s0
+/(vendor|system/vendor)/lib(64)?/hw/gralloc\.default\.so                              u:object_r:same_process_hal_file:s0
 
 #############################
 # Data files