x86: Use CR0 constants in CPU init

We should use these constants where possible.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

arch/x86/cpu/cpu.c

@@ -456,7 +456,7 @@ void x86_full_reset(void)
 
 int dcache_status(void)
 {
-	return !(read_cr0() & 0x40000000);
+	return !(read_cr0() & X86_CR0_CD);
 }
 
 /* Define these functions to allow ehch-hcd to function */