Move aarch64_linux_get_debug_reg_capacity to nat/aarch64-linux-hw-point.c

Move aarch64_linux_get_debug_reg_capacity to nat/aarch64-linux-hw-point.c

There are also some duplication on getting HW watchpoint/breakpoint
registers info between GDB and GDBserver.  This patch moves them
to nat/aarch64-linux-hw-point.c.

Note that ENABLE_NLS is not defined in GDBserver, so it should be OK
to use _( markup.

gdb:

2015-07-21  Yao Qi  <yao.qi@linaro.org>

	* aarch64-linux-nat.c (aarch64_linux_get_debug_reg_capacity):
	Move it to nat/aarch64-linux-hw-point.c.
	(aarch64_linux_child_post_startup_inferior): Update.
	* nat/aarch64-linux-hw-point.c (aarch64_linux_get_debug_reg_capacity):
	New function.
	* nat/aarch64-linux-hw-point.h (aarch64_linux_get_debug_reg_capacity):
	Declare it.

gdb/gdbserver:

2015-07-21  Yao Qi  <yao.qi@linaro.org>

	* linux-aarch64-low.c (aarch64_arch_setup): Remove code and call
	aarch64_linux_get_debug_reg_capacity.