[IA64] Guard elfcorehdr_addr with #if CONFIG_PROC_FS

Access to elfcorehdr_addr needs to be guarded by #if CONFIG_PROC_FS
as well as the existing #if guards.

Fixes the following build problem:

arch/ia64/hp/common/built-in.o: In function
`sba_init':arch/ia64/hp/common/sba_iommu.c:2043: undefined reference to `elfcorehdr_addr'
:arch/ia64/hp/common/sba_iommu.c:2043: undefined reference to `elfcorehdr_addr'
Signed-off-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/hp/common/sba_iommu.c

@@ -2034,7 +2034,8 @@ sba_init(void)
 	if (!ia64_platform_is("hpzx1") && !ia64_platform_is("hpzx1_swiotlb"))
 		return 0;
 
-#if defined(CONFIG_IA64_GENERIC) && defined(CONFIG_CRASH_DUMP)
+#if defined(CONFIG_IA64_GENERIC) && defined(CONFIG_CRASH_DUMP) && \
+        defined(CONFIG_PROC_FS)
 	/* If we are booting a kdump kernel, the sba_iommu will
 	 * cause devices that were not shutdown properly to MCA
 	 * as soon as they are turned back on.  Our only option for