x86, 64-bit: PSE no longer a hard requirement

Because Xen doesn't support PSE mappings in guests, all code which
assumed the presence of PSE has been changed to fall back to smaller
mappings if necessary.  As a result, PSE is optional rather than
required (though still used whereever possible).
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: xen-devel <xen-devel@lists.xensource.com>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/asm-x86/required-features.h

@@ -42,7 +42,7 @@
 #endif
 
 #ifdef CONFIG_X86_64
-#define NEED_PSE	(1<<(X86_FEATURE_PSE & 31))
+#define NEED_PSE	0
 #define NEED_MSR	(1<<(X86_FEATURE_MSR & 31))
 #define NEED_PGE	(1<<(X86_FEATURE_PGE & 31))
 #define NEED_FXSR	(1<<(X86_FEATURE_FXSR & 31))