MAINTAINERS: Add i.MX sdhci maintainer

Add myself as the i.MX sdhci driver maintainer.

Signed-off-by: Haibo Chen <haibo.chen@nxp.com>
Link: https://lore.kernel.org/r/1640076288-32714-1-git-send-email-haibo.chen@nxp.com


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>