coresight: Make current W=1 warnings default

coresight: Make current W=1 warnings default

Similarly to drivers/gpu/drm/amd/amdgpu/Makefile and
fs/btrfs/Makefile, copy the current set of W=1 warnings from
Makefile.extrawarn to the coresight makefile to make them default.
Unfortunately there is no easy way to do this without copying.

In addition to the default set of warnings, add -Wno-sign-compare to
disable that warning. That's because Makefile.extrawarn does some extra
steps to disable some -Wextra warnings unless W=2 or W=3 are used.
That's the only one that's needed for Coresight, so disable it.

Signed-off-by: James Clark <james.clark@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20231123120459.287578-5-james.clark@arm.com