mtd: Fixed checkpatch seq_printf warnings

Fixed checkpatch warnings: "WARNING: Prefer seq_puts to seq_printf"

This patch is created with reference to the ongoing lkml thread
https://lkml.org/lkml/2014/7/15/646
where Andrew Morton wrote:

"
- puts is presumably faster

- puts doesn't go rogue if you accidentally pass it a "%".

- this patch would actually make compiled object files few bytes smaller.
  Perhaps because seq_printf() is a varargs function, forcing the
  caller to pass args on the stack instead of in registers.
"

Signed-off-by: Samarth Parikh <samarthp@ymail.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>