spi/s3c64xx: Use devm_clk_get() and devm_request_irq()

Use devm_clk_get() and devm_request_irq() rather than clk_get() and
request_irq() to make cleanup paths more simple.

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>