ARM: shmobile: Remove obsolete custom earlyprintk code

The last caller of shmobile_setup_console() was removed in commit
44d88c75

 ("ARM: shmobile: Remove legacy SoC code for R-Mobile
A1").

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>