mtd: remove redundant dependency checks in Kconfig files

Look for dependency checks for "FOO" when inside of an "if FOO" block and remove them.

Signed-off-by: Kyle Spaans <kspaans@uwaterloo.ca>
Reviewed-by: Robert P. J. Day <rpjday@crashcourse.ca>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>