Centralize instruction-set pointer-size, alignment, 64b-width code
in instruction_set.h/cc

This allows to clean up some places that currently make explicit
comparisons.

Change-Id: I0dcc924c52fa53306f706aceea93a2d4a655c5df
diff --git a/compiler/driver/compiler_driver.cc b/compiler/driver/compiler_driver.cc
index 2b20c6f..0ad30be 100644
--- a/compiler/driver/compiler_driver.cc
+++ b/compiler/driver/compiler_driver.cc
@@ -339,7 +339,6 @@
       compiler_(Compiler::Create(compiler_kind)),
       instruction_set_(instruction_set),
       instruction_set_features_(instruction_set_features),
-      instruction_set_is_64_bit_(instruction_set == kX86_64 || instruction_set == kArm64),
       freezing_constructor_lock_("freezing constructor lock"),
       compiled_classes_lock_("compiled classes lock"),
       compiled_methods_lock_("compiled method lock"),
@@ -448,7 +447,7 @@
 }
 
 #define CREATE_TRAMPOLINE(type, abi, offset) \
-    if (instruction_set_is_64_bit_) { \
+    if (Is64BitInstructionSet(instruction_set_)) { \
       return CreateTrampoline64(instruction_set_, abi, \
                                 type ## _ENTRYPOINT_OFFSET(8, offset)); \
     } else { \