net: Kconfig whitespace cleanup

Many lines in Kconfig start withe 8 spaces instead of a TAB, and even
sometimes with 7 spaces.  Replace 10 or 9 spaces, or TAB + 1 space,
by TAB + 2 spaces, and 8 or 7 spaces by TAB.
Signed-off-by: Philippe De Muyter <phdm@macqel.be>
Signed-off-by: David S. Miller <davem@davemloft.net>