[SCSI] gdth: Remove 2.4.x support, in-kernel changelog

  * Remove in-source changelog.  It's archived permanently in git and
    various kernel archives, and changelogs should exist purely in git.

  * Remove 2.4.x kernel support.  It is an active obstacle to
    modernizing this driver, at this point.  This includes killing
    gdth_kcompat.h which is 100% redundant in modern kernels.

Signed-off-by: Jeff Garzik <jeff@garzik.org>
Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>