Minor changes to documentation and comments

Fix some typos and clarify some sentences.

Change-Id: Id276d1ced9a991b4eddc5c47ad9a825e6b29ef74
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
diff --git a/docs/arm-sip-service.rst b/docs/arm-sip-service.rst
index 9f0e266..6cdac83 100644
--- a/docs/arm-sip-service.rst
+++ b/docs/arm-sip-service.rst
@@ -4,7 +4,7 @@
 This document enumerates and describes the Arm SiP (Silicon Provider) services.
 
 SiP services are non-standard, platform-specific services offered by the silicon
-implementer or platform provider. They are accessed via. ``SMC`` ("SMC calls")
+implementer or platform provider. They are accessed via ``SMC`` ("SMC calls")
 instruction executed from Exception Levels below EL3. SMC calls for SiP
 services: