cortex_a9: move dap_ap_select to arm_avi_v5

cortex_a9: move dap_ap_select to arm_avi_v5

dap_ap_select was used in the code at various points, but that can lead to
confusion, without any knowledge of what AP is really selected at some
points.
Some bugs derive from this (for example md/mw doesn't work well after
issueing "dap apsel" command).
Moving it to arm_adi_v5.c (using  mem_ap_sel* functions instead of mem_ap_*)
make the code more clear and more easier to maintain.
In the future it should be made "static" to avoid its use outside arm_adi_v5

One further benefit is the various goto has been removed as well

Signed-off-by: Luca Ellero <lroluk@gmail.com>