ARC: [DeviceTree] Convert some Kconfig items to runtime values

* mem size now runtime configured (prev CONFIG_ARC_PLAT_SDRAM_SIZE)
* core cpu clk runtime configured (prev CONFIG_ARC_PLAT_CLK)

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Grant Likely <grant.likely@secretlab.ca>

diff --cc arch/arc/Kconfig
Simple merge

diff --cc arch/arc/boot/dts/skeleton.dtsi
Simple merge

diff --cc arch/arc/include/asm/clk.h
Simple merge

diff --cc arch/arc/kernel/clk.c
Simple merge

diff --cc arch/arc/kernel/devtree.c
Simple merge

diff --cc arch/arc/mm/init.c
Simple merge