ata: ahci: remove bad free

ata: ahci: remove bad free

In the case of a memory allocation error, the ahci_port_start() function
tries to free the `pp' pointer.
This pointer was not dynamically allocated but does in fact point to an
element of the port[] array member of the struct ahci_uc_priv.
Remove the erroneous call to free() to fix this.

Fixes: 4782ac80b02f ("Add AHCI support to u-boot")
Signed-off-by: Vincent Stehlé <vincent.stehle@arm.com>
Cc: Tom Rini <trini@konsulko.com>
Cc: Jason Jin <jason.jin@freescale.com>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>