x86: Move qemu CPU fixup function into its own file

This function is specific to qemu so it seems best to keep it separate
from the generic code.

Move it out to a new file and update the condition to use if() instead of
 #ifdef

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/include/qfw.h b/include/qfw.h
index 2f1a204..cea8e11 100644
--- a/include/qfw.h
+++ b/include/qfw.h
@@ -172,4 +172,12 @@
 bool qemu_fwcfg_present(void);
 bool qemu_fwcfg_dma_present(void);
 
+/**
+ * qemu_cpu_fixup() - Fix up the CPUs for QEMU
+ *
+ * @return 0 if OK, -ENODEV if no CPUs, -ENOMEM if out of memory, other -ve on
+ *	on other error
+ */
+int qemu_cpu_fixup(void);
+
 #endif