xen/arm: add lower-bound check in mfn_valid

mfn_valid only checks the upper-bound of mfn (max_page).
Add the lower-bound check of mfn (frametable_base_mfn).

Signed-off-by: Jaeyong Yoo <jaeyong.yoo@samsung.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Julien Grall <julien.grall@linaro.org>

xen/include/asm-arm/mm.h

@@ -190,7 +190,7 @@ static inline void __iomem *ioremap_wc(paddr_t start, size_t len)
 
 #define mfn_valid(mfn)        ({                                              \
     unsigned long __m_f_n = (mfn);                                            \
-    likely(__m_f_n < max_page);                                               \
+    likely(__m_f_n >= frametable_base_mfn && __m_f_n < max_page);             \
 })
 
 #define max_pdx                 max_page