csky: change a Kconfig symbol name to fix e1000 build error

e1000's #define of CONFIG_RAM_BASE conflicts with a Kconfig symbol in
arch/csky/Kconfig.

The symbol in e1000 has been around longer, so change arch/csky/ to use
DRAM_BASE instead of RAM_BASE to remove the conflict. (although e1000
is also a 2-line change)

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Randy Dunlap <[e-mail]>
Reported-by: kernel test robot <[e-mail]>
Acked-by: Guo Ren <[e-mail]>
Cc: Jesse Brandeburg <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/csky/Kconfig

···
 	int "Maximum zone order"
 	default "11"
 
-config RAM_BASE
+config DRAM_BASE
 	hex "DRAM start addr (the same with memory-section in dts)"
 	default 0x0
 

arch/csky/include/asm/page.h

···
 #define SSEG_SIZE	0x20000000
 #define LOWMEM_LIMIT	(SSEG_SIZE * 2)
 
-#define PHYS_OFFSET_OFFSET (CONFIG_RAM_BASE & (SSEG_SIZE - 1))
+#define PHYS_OFFSET_OFFSET (CONFIG_DRAM_BASE & (SSEG_SIZE - 1))
 
 #ifndef __ASSEMBLY__