arm_adi_v5: add API send_sequence() and use it

arm_adi_v5: add API send_sequence() and use it

The method to send an arbitrary sequence to DAP depends on the
transport and is thus different on JTAG and SWD. This is already
coded in dap_to_jtag() and dap_to_swd().

Add a new API send_sequence() in struct dap_ops.
Add the implementations of send_sequence() in adi_v5_jtag.c and
adi_v5_swd.c
Rewrite dap_to_jtag() and dap_to_swd() using the new API.
Move the enum swd_special_seq in arm_adi_v5.h to solve a circular
dependencies among swd.h and arm_adi_v5.h

Change-Id: I9db13a00f129761eab283783c094cfff2dd92610
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/4902
Tested-by: jenkins
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>