payloads/coreinfo/README: Use `It is` instead of `Its`

Change-Id: Ic1a9f2f01c26ee97cd7183fcf1755cb916f1b02e
Signed-off-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-on: http://review.coreboot.org/5704
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>
diff --git a/payloads/coreinfo/README b/payloads/coreinfo/README
index 4df5359..0c41452 100644
--- a/payloads/coreinfo/README
+++ b/payloads/coreinfo/README
@@ -1,5 +1,5 @@
 This is a silly little program that demonstrates how cool libpayload is
-and also serves a purpose.  Its fun and educational!
+and also serves a purpose.  It is fun and educational!
 
 Requirements
 ------------