ARM: OMAP4: hsmmc: check for null pointer

platform_device pdev can be NULL if CONFIG_MMC_OMAP_HS is not set.
Add check for NULL pointer. while at it move the duplicated functions
to omap4-common.c

Fixes the following boot crash seen with omap4sdp and omap4panda
when MMC is disabled.

Unable to handle kernel NULL pointer dereference at virtual address 0000008c
pgd = c0004000
[0000008c] *pgd=00000000
Internal error: Oops: 5 [#1] SMP ARM
Modules linked in:
CPU: 0    Not tainted  (3.4.0-rc1-05971-ga4dfa82 #4)
PC is at omap_4430sdp_init+0x184/0x410
LR is at device_add+0x1a0/0x664

Signed-off-by: Balaji T K <balajitk@ti.com>
Reported-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
diff --git a/arch/arm/mach-omap2/common.h b/arch/arm/mach-omap2/common.h
index 57da7f4..c09ca63 100644
--- a/arch/arm/mach-omap2/common.h
+++ b/arch/arm/mach-omap2/common.h
@@ -27,6 +27,7 @@
 #ifndef __ASSEMBLER__
 
 #include <linux/delay.h>
+#include <linux/i2c/twl.h>
 #include <plat/common.h>
 #include <asm/proc-fns.h>
 
@@ -254,6 +255,8 @@
 struct omap_sdrc_params;
 extern void omap_sdrc_init(struct omap_sdrc_params *sdrc_cs0,
 				      struct omap_sdrc_params *sdrc_cs1);
+struct omap2_hsmmc_info;
+extern int omap4_twl6030_hsmmc_init(struct omap2_hsmmc_info *controllers);
 
 #endif /* __ASSEMBLER__ */
 #endif /* __ARCH_ARM_MACH_OMAP2PLUS_COMMON_H */