u functions

This patch adds flush_write_buffers() in some functions of pci-nommu_64.c
They are added anywhere i386 would also have it. This is not a problem
for x86_64, since flush_rite_buffers() an nop for it.

Signed-off-by: Glauber Costa <gcosta@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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