Fix build

Actually some systems don't define PAGE_SIZE. Fixes build breakage
by f7736b91.
Signed-off-by: NBlue Swirl <blauwirbel@gmail.com>

hw/ide/core.c

@@ -34,6 +34,8 @@
 
 #include <hw/ide/internal.h>
 
+#define IDE_PAGE_SIZE 4096
+
 static int smart_attributes[][5] = {
     /* id,  flags, val, wrst, thrsh */
     { 0x01, 0x03, 0x64, 0x64, 0x06}, /* raw read */
@@ -433,13 +435,13 @@ static int dma_buf_prepare(BMDMAState *bm, int is_write)
     } prd;
     int l, len;
 
-    qemu_sglist_init(&s->sg, s->nsector / (PAGE_SIZE / 512) + 1);
+    qemu_sglist_init(&s->sg, s->nsector / (IDE_PAGE_SIZE / 512) + 1);
     s->io_buffer_size = 0;
     for(;;) {
         if (bm->cur_prd_len == 0) {
             /* end of table (with a fail safe of one page) */
             if (bm->cur_prd_last ||
-                (bm->cur_addr - bm->addr) >= PAGE_SIZE)
+                (bm->cur_addr - bm->addr) >= IDE_PAGE_SIZE)
                 return s->io_buffer_size != 0;
             cpu_physical_memory_read(bm->cur_addr, (uint8_t *)&prd, 8);
             bm->cur_addr += 8;
@@ -522,7 +524,7 @@ static int dma_buf_rw(BMDMAState *bm, int is_write)
         if (bm->cur_prd_len == 0) {
             /* end of table (with a fail safe of one page) */
             if (bm->cur_prd_last ||
-                (bm->cur_addr - bm->addr) >= PAGE_SIZE)
+                (bm->cur_addr - bm->addr) >= IDE_PAGE_SIZE)
                 return 0;
             cpu_physical_memory_read(bm->cur_addr, (uint8_t *)&prd, 8);
             bm->cur_addr += 8;