SD/MMC on Colibri iMX7S/D modules successfully support
200Mhz frequency in HS200 mode.

Removing the unnecessary max-frequency limit significantly
increases the performance:

== before fix ====
root@colibri-imx7-emmc:~# hdparm -t /dev/mmcblk0
/dev/mmcblk0:
 Timing buffered disk reads: 252 MB in  3.02 seconds =  83.54 MB/sec
==================

=== after fix ====
root@colibri-imx7-emmc:~# hdparm -t /dev/mmcblk0
/dev/mmcblk0:
 Timing buffered disk reads: 408 MB in  3.00 seconds = 135.94 MB/sec
==================

Fixes: f928a4a3 ("ARM: dts: imx7: add Toradex Colibri iMX7D 1GB (eMMC) support")
Signed-off-by: Oleksandr Suvorov <oleksandr.suvorov@toradex.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>