MAINTAINERS: mmc: sdhci-of-at91: handover maintenance to Eugen Hristev

As Eugen handles the software for bootloaders and new products, handover
the maintenance to him.

Signed-off-by: Ludovic Desroches <ludovic.desroches@microchip.com>
Acked-by: Eugen Hristev <eugen.hristev@microchip.com>
Link: https://lore.kernel.org/r/20200709085331.8145-1-ludovic.desroches@microchip.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>