gdb: remove some unnecessary watchpoint_addr_within_range overrides

gdb: remove some unnecessary watchpoint_addr_within_range overrides

While looking at the watchpoint code, I realised that AArch64, ARM,
and Loongarch all override watchpoint_addr_within_range with an
implementation that is the same as the default (but with the logic
written slightly differently).

Compare the deleted functions to default_watchpoint_addr_within_range
in target.c.

The only other targets that override watchpoint_addr_within_range are
ppc_linux_nat_target and remote_target, in both cases the
implementation is different to the default.

Lets remove these unnecessary overrides, and just use the default.

There should be no user visible changes after this commit.

Approved-By: Simon Marchi <simon.marchi@efficios.com>