ARM: SAMSUNG: remove unused SPI clock headers

Commit 875a5937 ("ARM: SAMSUNG:
Consolidation of SPI platform devices to plat-samsung") deleted all
(four) files that included one of the "spi-clocks.h" headers. It seems
it was just an oversight to not remove those headers too. They can
safely be removed now.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>