clockevents/drivers/sh_cmt: Remove obsolete sh-cmt-48-gen2 platform_device_id entry

Since commit 914d7d14 ("ARM: shmobile: r8a73a4: Remove legacy
code"), all former users of the "sh-cmt-48-gen2" platform device name
are only supported in generic DT-only ARM multi-platform builds.  The
driver doesn't need to match platform devices by name anymore, hence
remove the corresponding platform_device_id entry.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Acked-by: Simon Horman <horms+renesas@verge.net.au>