vexpress64: Refactor header file to make it easier to add new FVPs

Rename from vexpress_aemv8a.h -> vepxress_aemv8.h as new FVPs may not be
v8-A. No change in behavior.

This is towards future work to enable support for the FVP_BaseR.

Signed-off-by: Peter Hoyes <Peter.Hoyes@arm.com>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
diff --git a/doc/README.semihosting b/doc/README.semihosting
index c019999..f382d01 100644
--- a/doc/README.semihosting
+++ b/doc/README.semihosting
@@ -25,7 +25,7 @@
 Rather than create a new armv8 board similar to armltd/vexpress64, add
 semihosting calls to the existing one, enabled with CONFIG_SEMIHOSTING
 and CONFIG_BASE_FVP both set. Also reuse the existing board config file
-vexpress_aemv8a.h but differentiate the two models by the presence or
+vexpress_aemv8.h but differentiate the two models by the presence or
 absence of CONFIG_BASE_FVP. This change is tested and works on both the
 Foundation and Base fastmodel simulators.