mtd: davinci_nand: Use managed resources

davinci_nand driver currently uses normal kzalloc, ioremap and get_clk
routines. This patch replaces these routines with devm_kzalloc,
devm_request_and_ioremap and devm_clk_get resp.

Signed-off-by: Mrugesh Katepallewar <mrugesh.mk@ti.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>