drm/print: Fixup DRM_DEBUG_KMS_RATELIMITED()

Since we're about to move drm_dp_helper.c over to drm_dbg_*(), we'll want
to make sure that we can also add ratelimited versions of these macros in
order to retain some of the previous debugging output behavior we had.

However, as I was preparing to do this I noticed that the current
rate limited macros we have are kind of bogus. It looks like when I wrote
these, I didn't notice that we'd always be calling __ratelimit() even if
the debugging message we'd be printing would normally be filtered out due
to the relevant DRM debugging category being disabled.

So, let's fix this by making sure to check drm_debug_enabled() in our
ratelimited macros before calling __ratelimit(), and start using
drm_dev_printk() in order to print debugging messages since that will save
us from doing a redundant drm_debug_enabled() check. And while we're at it,
let's move the code for this into another macro that we can reuse for
defining new ratelimited DRM debug macros more easily.

v2:
* Make sure to use tabs where possible in __DRM_DEFINE_DBG_RATELIMITED()

Signed-off-by: Lyude Paul <lyude@redhat.com>
Cc: Robert Foss <robert.foss@linaro.org>
Reviewed-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210326203807.105754-8-lyude@redhat.com