AMD CIMx SB800: Update Kconfig help texts to new SATA mode default

In the following commit

    commit ee5c111755ac4acc6dfb6e10a4e271211e149a39
    Author: Paul Menzel <paulepanter@users.sourceforge.net>
    Date:   Tue Mar 12 12:41:40 2013 +0100

        AMD CIMx SB800: Enable AHCI mode for SATA controller by default

        Reviewed-on: http://review.coreboot.org/2661

I forgot to update the help texts to the new SATA mode default. Do
so now.

Additionally note that help texts for `choice` do not seem to be
shown.

Change-Id: I17f401633a2136efca2b21a621482e0724ff9f04
Signed-off-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-on: http://review.coreboot.org/2936
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
1 file changed