[ARM] pxa: use kzalloc() in pxa_init_gpio_chip()

As slab is available early now, use kzalloc() rather than
alloc_bootmem_low() in pxa_init_gpio_chip().

This removes the following boot time warning:

<4>------------[ cut here ]------------
<4>WARNING: at mm/bootmem.c:535 alloc_arch_preferred_bootmem+0x2c/0x54()
<d>Modules linked in:
[<c0029430>] (unwind_backtrace+0x0/0xdc) from [<c0036f64>] (warn_slowpath_common+0x4c/0x80)
[<c0036f64>] (warn_slowpath_common+0x4c/0x80) from [<c000ede0>] (alloc_arch_preferred_bootmem+0x2c/0x54)
[<c000ede0>] (alloc_arch_preferred_bootmem+0x2c/0x54) from [<c000f2e4>] (___alloc_bootmem_nopanic+0x34/0xd0)
[<c000f2e4>] (___alloc_bootmem_nopanic+0x34/0xd0) from [<c000f6e4>] (___alloc_bootmem+0xc/0x34)
[<c000f6e4>] (___alloc_bootmem+0xc/0x34) from [<c000cb20>] (pxa_init_gpio+0x48/0x228)
[<c000cb20>] (pxa_init_gpio+0x48/0x228) from [<c0009794>] (init_IRQ+0x34/0x44)
[<c0009794>] (init_IRQ+0x34/0x44) from [<c00089d4>] (start_kernel+0x144/0x264)
[<c00089d4>] (start_kernel+0x144/0x264) from [<a0008034>] (0xa0008034)
<4>---[ end trace 1b75b31a2719ed1c ]---

Signed-off-by: Daniel Mack <daniel@caiaq.de>
Signed-off-by: Eric Miao <eric.y.miao@gmail.com>

arch/arm/plat-pxa/gpio.c

@@ -16,7 +16,7 @@
 #include <linux/irq.h>
 #include <linux/io.h>
 #include <linux/sysdev.h>
-#include <linux/bootmem.h>
+#include <linux/slab.h>
 
 #include <mach/gpio.h>
 
@@ -112,17 +112,12 @@ static int __init pxa_init_gpio_chip(int gpio_end)
 	int i, gpio, nbanks = gpio_to_bank(gpio_end) + 1;
 	struct pxa_gpio_chip *chips;
 
-	/* this is early, we have to use bootmem allocator, and we really
-	 * want this to be allocated dynamically for different 'gpio_end'
-	 */
-	chips = alloc_bootmem_low(nbanks * sizeof(struct pxa_gpio_chip));
+	chips = kzalloc(nbanks * sizeof(struct pxa_gpio_chip), GFP_KERNEL);
 	if (chips == NULL) {
 		pr_err("%s: failed to allocate GPIO chips\n", __func__);
 		return -ENOMEM;
 	}
 
-	memset(chips, 0, nbanks * sizeof(struct pxa_gpio_chip));
-
 	for (i = 0, gpio = 0; i < nbanks; i++, gpio += 32) {
 		struct gpio_chip *c = &chips[i].chip;