AHCI: remove obsolete free_contig calls
AHCI: remove obsolete free_contig calls

The memory used to be in its own memory region, but is now a part of
a larger memory region which is already being freed anyway.

Change-Id: Ice3174cec76e07112a1997b969dc3f47f573514c

veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi