selinux: Label misc block device.

Suppress the following warnings when calling uncrypt.

avc: granted { write } for name="mmcblk0p23" dev="tmpfs" ino=10885 scontext=u:r:uncrypt:s0 tcontext=u:object_r:block_device:s0 tclass=blk_file
avc: granted { write open } for path="/dev/block/mmcblk0p23" dev="tmpfs" ino=10885 scontext=u:r:uncrypt:s0 tcontext=u:object_r:block_device:s0 tclass=blk_file

Bug: 25091603
Change-Id: Ib41a144e69d9b234ab88875734b28bc85e17a7ad
diff --git a/sepolicy/file_contexts b/sepolicy/file_contexts
index 97eb97a..2ae8be8 100644
--- a/sepolicy/file_contexts
+++ b/sepolicy/file_contexts
@@ -50,6 +50,7 @@
 /dev/block/platform/soc\.0/f9824900\.sdhci/by-name/ssd          u:object_r:ssd_block_device:s0
 /dev/block/platform/soc\.0/f9824900\.sdhci/by-name/metadata     u:object_r:metadata_block_device:s0
 /dev/block/platform/soc\.0/f9824900\.sdhci/by-name/recovery     u:object_r:recovery_block_device:s0
+/dev/block/platform/soc\.0/f9824900\.sdhci/by-name/misc         u:object_r:misc_block_device:s0
 
 /dev/subsys_.*                         u:object_r:ssr_device:s0
 /dev/ramdump_.*                        u:object_r:ramdump_device:s0