usb: gadget: ncm: Fix indentations in documentation of NCM section

Currently, the section of NCM which describes attributes are having wrong
indentation.

Fix this by following the correct format recommended.

Fixes: 1900daeefd3e ("usb: gadget: ncm: Add support to update wMaxSegmentSize via configfs")
Reported-by: Stephen Rothwell <[e-mail]>
Closes: https://lore.kernel.org/all/[e-mail]/
Signed-off-by: Udipto Goswami <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/usb/gadget-testing.rst

···
 The function name to use when creating the function directory is "ncm".
 The NCM function provides these attributes in its function directory:
 
-	===============   ==================================================
-	ifname		  network device interface name associated with this
-			  function instance
-	qmult		  queue length multiplier for high and super speed
-	host_addr	  MAC address of host's end of this
-			  Ethernet over USB link
-	dev_addr	  MAC address of device's end of this
-			  Ethernet over USB link
-	max_segment_size  Segment size required for P2P connections. This
-			  will set MTU to (max_segment_size - 14 bytes)
-	===============   ==================================================
+	======================= ==================================================
+	ifname			network device interface name associated with this
+				function instance
+	qmult			queue length multiplier for high and super speed
+	host_addr		MAC address of host's end of this
+				Ethernet over USB link
+	dev_addr		MAC address of device's end of this
+				Ethernet over USB link
+	max_segment_size	Segment size required for P2P connections. This
+				will set MTU to 14 bytes
+	======================= ==================================================
 
 and after creating the functions/ncm.<instance name> they contain default
 values: qmult is 5, dev_addr and host_addr are randomly selected.