EDAC/i5400: Fix snprintf() limit calculation in calculate_dimm_size()

The snprintf() can't really overflow because we're writing a max of 42
bytes to a PAGE_SIZE buffer.  But my static checker complains because
the limit calculation doesn't take the first 11 space characters that
we wrote into the buffer into consideration.  Fix this for the sake of
correctness even though it doesn't affect runtime.

Also delete an earlier "space -= n;" which was not used.

Fixes: 68d086f ("i5400_edac: improve debug messages to better represent the filled memory")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Link: https://patch.msgid.link/ccd06b91748e7ed8e33eeb2ff1e7b98700879304.1765290801.git.dan.carpenter@linaro.org

Author: Dan Carpenter

drivers/edac/i5400_edac.c

@@ -1026,13 +1026,13 @@ static void calculate_dimm_size(struct i5400_pvt *pvt)
 		space -= n;
 	}
 
-	space -= n;
 	edac_dbg(2, "%s\n", mem_buffer);
 	p = mem_buffer;
 	space = PAGE_SIZE;
 
 	n = snprintf(p, space, "           ");
 	p += n;
+	space -= n;
 	for (branch = 0; branch < MAX_BRANCHES; branch++) {
 		n = snprintf(p, space, "       branch %d       | ", branch);
 		p += n;