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

Since the removal of the r8a7740 legacy SoC code in commit
44d88c75

 ("ARM: shmobile: Remove legacy SoC code for R-Mobile
A1"), 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>
(cherry picked from commit 8c436f84

)
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>