mmc: queue: remove redundant memsets

Not needed to memset, as they are pointers and are assigned
to proper values in the next line anyway.

Signed-off-by: Venkatraman S <svenkatr@ti.com>
Reviewed-by: Namjae Jeon <linkinjeon@gmail.com>
Signed-off-by: Chris Ball <cjb@laptop.org>