flash: retire unused eCos flash driver

even the AT91EB40a's flash is covered by CFI and nobody ever submitted
any other drivers based on eCos code. It's just possible that this
idea was missing documentation and "marketing", but it's in git if
somebody wants to resurrect it.

Change-Id: I66449aa6e0997301f9d67f28098789bfc891d6e9
Signed-off-by: Øyvind Harboe <oyvind.harboe@zylin.com>
Reviewed-on: http://openocd.zylin.com/502


Tested-by: jenkins
Reviewed-by: Øyvind Harboe <oyvindharboe@gmail.com>