Add bootloader_prop for ro.boot. properties

ro.boot. properties assigned as "exported2_default_prop" are now
"bootloader_prop", to remove bad context name "exported2_default_prop".

Two things to clarify:

1) We have both the prefix entry and the exact entries. Although the
exact entries may be redundant, we may want to keep them. Vendors are
still allowed to have properties starting with "ro.boot." on
vendor_property_contexts file. The exact entries can prevent vendors
from modifying them to random contexts.

2) ro.boot. is special as it is originally for kernel command line
"androidboot.". But some ro.boot. properties are being used as if they
were normal. To avoid regression, ro.boot. properties having contexts
other than "exported2_default_prop" are not changed here. They will be
tracked later.

Bug: 155844385
Test: m selinux_policy
Change-Id: Ic0f4117ae68a828787304187457b5e1e105a52c7
Merged-In: Ic0f4117ae68a828787304187457b5e1e105a52c7
diff --git a/private/compat/30.0/30.0.cil b/private/compat/30.0/30.0.cil
index 6a6348a..7f96179 100644
--- a/private/compat/30.0/30.0.cil
+++ b/private/compat/30.0/30.0.cil
@@ -1348,6 +1348,7 @@
 (typeattributeset exported2_default_prop_30_0
   ( exported2_default_prop
     aac_drc_prop
+    bootloader_prop
     build_prop
     init_service_status_prop
     libc_debug_prop))