Allow hwcomposer to change scheduling policy

Bug: 35210697
Test: manual
Change-Id: I0e1e8923851f668d5fe6c210f411a8e4ff0470c7

public/hal_graphics_composer.te

@@ -14,3 +14,6 @@ allow hal_graphics_composer graphics_device:chr_file rw_file_perms;
 allow hal_graphics_composer system_server:fd use;
 allow hal_graphics_composer bootanim:fd use;
 allow hal_graphics_composer appdomain:fd use;
+
+# allow self to set SCHED_FIFO
+allow hal_graphics_composer self:capability sys_nice;