src/include: Indent code using tabs

Fix the following error and warning detected by checkpatch.pl:

ERROR: code indent should use tabs where possible
WARNING: please, no spaces at the start of a line

TEST=Build and run on Galileo Gen2

Change-Id: I487771b8f4d7e104457116b772cd32df5cd721a6
Signed-off-by: Lee Leahy <Leroy.P.Leahy@intel.com>
Reviewed-on: https://review.coreboot.org/18646
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>

src/include/cbmem.h

@@ -52,7 +52,7 @@ struct cbmem_entry;
 /* Determine the size for CBMEM root and the small allocations */
 static inline size_t cbmem_overhead_size(void)
 {
-   return 2 * CBMEM_ROOT_MIN_SIZE;
+	return 2 * CBMEM_ROOT_MIN_SIZE;
 }
 
 /* By default cbmem is attempted to be recovered. Returns 0 if cbmem was