s390/pci: cleanup clp page allocation

Use the __get_free_pages wrapper in clp_alloc_block. Also change the
allocation to use one page only. This page is used as CLP response
block e.g. to list available pci functions. Using one page we can
list > 250 pci functions at once and we have code to loop around this
CLP command (if not all functions fit into to the CLP block) already
in place.
Acked-by: NGerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: NSebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/clp.h

@@ -2,7 +2,7 @@
 #define _ASM_S390_CLP_H
 
 /* CLP common request & response block size */
-#define CLP_BLK_SIZE			(PAGE_SIZE * 2)
+#define CLP_BLK_SIZE			PAGE_SIZE
 
 struct clp_req_hdr {
 	u16 len;

arch/s390/pci/pci_clp.c

@@ -37,8 +37,7 @@ static inline u8 clp_instr(void *data)
 
 static void *clp_alloc_block(void)
 {
-	struct page *page = alloc_pages(GFP_KERNEL, get_order(CLP_BLK_SIZE));
-	return (page) ? page_address(page) : NULL;
+	return (void *) __get_free_pages(GFP_KERNEL, get_order(CLP_BLK_SIZE));
 }
 
 static void clp_free_block(void *ptr)