target/arm: Move define_debug_regs() to debug_helper.c

target/arm: Move define_debug_regs() to debug_helper.c

The target/arm/helper.c file is very long and is a grabbag of all
kinds of functionality.  We have already a debug_helper.c which has
code for implementing architectural debug.  Move the code which
defines the debug-related system registers out to this file also.
This affects the define_debug_regs() function and the various
functions and arrays which are used only by it.

The functions raw_write() and arm_mdcr_el2_eff() and
define_debug_regs() now need to be global rather than local to
helper.c; everything else is pure code movement.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20220630194116.3438513-3-peter.maydell@linaro.org