Fix cortex-a-rt docs title.

Also clarify that both only apply to AArch32 systems. The terms 'Cortex-R'
and 'Cortex-A' are particular brands of processor made by Arm, and there
are processors under each of those brands that run in (or only run in)
AArch64 mode.

Author: jonathanpallant

cortex-a-rt/src/lib.rs

@@ -1,4 +1,4 @@
-//! # Run-time support for Arm Cortex-R
+//! # Run-time support for Arm Cortex-A (AArch32)
 //!
 //! This library implements a simple Arm vector table, suitable for getting into
 //! a Rust application running in System Mode. It also provides a reference

cortex-r-rt/src/lib.rs

@@ -1,4 +1,4 @@
-//! # Run-time support for Arm Cortex-R
+//! # Run-time support for Arm Cortex-R (AArch32)
 //!
 //! This library implements a simple Arm vector table, suitable for getting into
 //! a Rust application running in System Mode. It also provides a reference