sim: Use named constants for pseudo ops

Use named constants from a shared header instead of magic values when
handling pseudo ops.

Change-Id: If157060bbcd772ce7e8556482b44ca714f4319b1
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/4262
Reviewed-by: Gabe Black <gabeblack@google.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>

SConstruct

diff --git a/SConstruct b/SConstruct
index 146b156..e4880e1 100755
--- a/SConstruct
+++ b/SConstruct
@@ -554,6 +554,9 @@
 # the ext directory should be on the #includes path
 main.Append(CPPPATH=[Dir('ext')])
 
+# Add shared top-level headers
+main.Prepend(CPPPATH=Dir('include'))
+
 def strip_build_path(path, env):
     path = str(path)
     variant_base = env['BUILDROOT'] + os.path.sep