hla: move memory read/write functionality to driver

hla: move memory read/write functionality to driver

Due to issues reported when using the jtag mode of the stlink (see Trac #61),
the functionality/checking has been moved to the driver.

This change also fixes unaligned 32bit memory read/write for the stlink.

From testing this change also brings a 3KiB/s speed increase, this is due
to the larger read/write packets.

Change-Id: I8234110e7e49a683f4dadd54c442ecdc3c47b320
Signed-off-by: Spencer Oliver <spen@spen-soft.co.uk>
Reviewed-on: http://openocd.zylin.com/1632
Tested-by: jenkins
Reviewed-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>