LoongArch: Adapted SECTION_SIZE_BITS with page size

LoongArch inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I6BWFP

--------------------------------
Signed-off-by: Nzhangtianyang <zhangtianyang@loongson.cn>
Change-Id: Ib32d4a2fc458fedd939e76e86d8bdddfe3c43914

arch/loongarch/include/asm/sparsemem.h

@@ -8,7 +8,7 @@
  * SECTION_SIZE_BITS		2^N: how big each section will be
  * MAX_PHYSMEM_BITS		2^N: how much memory we can have in that space
  */
-#define SECTION_SIZE_BITS	29 /* 2^29 = Largest Huge Page Size */
+#define SECTION_SIZE_BITS	28
 #define MAX_PHYSMEM_BITS	48
 
 #ifndef CONFIG_SPARSEMEM_VMEMMAP