x86, range: fix missing merge during add range

Christian found v3.9 does not work with E350 with EFI is enabled.

[ 1.658832] Trying to unpack rootfs image as initramfs...
[ 1.679935] BUG: unable to handle kernel paging request at ffff88006e3fd000
[ 1.686940] IP: [<ffffffff813661df>] memset+0x1f/0xb0
[ 1.692010] PGD 1f77067 PUD 1f7a067 PMD 61420067 PTE 0

but early memtest report all memory could be accessed without problem.

early page table is set in following sequence:
[ 0.000000] init_memory_mapping: [mem 0x00000000-0x000fffff]
[ 0.000000] init_memory_mapping: [mem 0x6e600000-0x6e7fffff]
[ 0.000000] init_memory_mapping: [mem 0x6c000000-0x6e5fffff]
[ 0.000000] init_memory_mapping: [mem 0x00100000-0x6bffffff]
[ 0.000000] init_memory_mapping: [mem 0x6e800000-0x6ea07fff]
but later efi_enter_virtual_mode try set mapping again wrongly.
[ 0.010644] pid_max: default: 32768 minimum: 301
[ 0.015302] init_memory_mapping: [mem 0x640c5000-0x6e3fcfff]
that means it fails with pfn_range_is_mapped.

It turns out that we have a bug in add_range_with_merge and it does not
merge range properly when new add one fill the hole between two exsiting
ranges. In the case when [mem 0x00100000-0x6bffffff] is the hole between
[mem 0x00000000-0x000fffff] and [mem 0x6c000000-0x6e7fffff].

Fix the add_range_with_merge by calling itself recursively.

Reported-by: "Christian König" <[e-mail]>
Signed-off-by: Yinghai Lu <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Cc: <[e-mail]> v3.9
Signed-off-by: H. Peter Anvin <[e-mail]>

kernel/range.c

···
 		final_start = min(range[i].start, start);
 		final_end = max(range[i].end, end);
 
-		range[i].start = final_start;
-		range[i].end =  final_end;
-		return nr_range;
+		/* clear it and add it back for further merge */
+		range[i].start = 0;
+		range[i].end =  0;
+		return add_range_with_merge(range, az, nr_range,
+			final_start, final_end);
 	}
 
 	/* Need to add it: */