MAINTAINERS: at91: remove the TC entry

MAINTAINERS: at91: remove the TC entry

"MICROCHIP TIMER COUNTER (TC) AND CLOCKSOURCE DRIVERS" is better
removed because one file entry is outdated and basically, the
maintainer's pool of Alexandre, Ludovic and myself is better suited.

drivers/misc/atmel_tclib.c file is going away in a patch to come and
drivers/clocksource/tcb_clksrc.c file is actually named timer-atmel-tcb.c.
This new name matches the AT91 entry regular expression.

Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Link: https://lore.kernel.org/r/20190823083158.2649-2-nicolas.ferre@microchip.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>