target: algorithm: change reg_name to const in init_reg_param()

target: algorithm: change reg_name to const in init_reg_param()

The function init_reg_param() initializes a struct where the
pointer reg_name is assigned to a 'const char *'.

Change the prototype of init_reg_param() to make also the reg_name
parameter as 'const char *'.

Change-Id: Ib999eaa5786ad24aa2a361070162c6f362784758
Reported-by: Marek Kraus <gamelaster@outlook.com>
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/8797
Tested-by: jenkins
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-by: Marek Kraus <gamelaster@outlook.com>