Correct some spellings.

Test: mma
Change-Id: Icc49a4ee76f12d302ed18982d334f2f70b7263a8
diff --git a/common/boot_control_stub.h b/common/boot_control_stub.h
index 7832adc..9e3b05c 100644
--- a/common/boot_control_stub.h
+++ b/common/boot_control_stub.h
@@ -27,7 +27,7 @@
 // typically used when e.g. an underlying HAL implementation cannot be
 // loaded or doesn't exist.
 //
-// You are gauranteed that the implementation of GetNumSlots() method
+// You are guaranteed that the implementation of GetNumSlots() method
 // always returns 0. This can be used to identify that this
 // implementation is in use.
 class BootControlStub : public BootControlInterface {