ARM: davinci: always enable CONFIG_ARCH_DAVINCI_DA850

ARM: davinci: always enable CONFIG_ARCH_DAVINCI_DA850

A change to the clk driver broke configurations that enable DA830
but not DA850:

arm-linux-gnueabi-ld: drivers/clk/davinci/pll.o: in function `__da850_pll0_of_clk_init_declare':
pll.c:(.init.text+0x30): undefined reference to `of_da850_pll0_init'
arm-linux-gnueabi-ld: drivers/clk/davinci/pll.o:(.rodata.davinci_pll_id_table+0x14): undefined reference to `da850_pll0_init'
arm-linux-gnueabi-ld: drivers/clk/davinci/pll.o:(.rodata.davinci_pll_id_table+0x2c): undefined reference to `da850_pll1_init'
arm-linux-gnueabi-ld: drivers/clk/davinci/pll.o:(.rodata.davinci_pll_of_match+0xc0): undefined reference to `of_da850_pll1_init'
arm-linux-gnueabi-ld: drivers/clk/davinci/psc.o:(.rodata.davinci_psc_id_table+0x14): undefined reference to `da850_psc0_init_data'
arm-linux-gnueabi-ld: drivers/clk/davinci/psc.o:(.rodata.davinci_psc_id_table+0x2c): undefined reference to `da850_psc1_init_data'

Select ARCH_DAVINCI_DA850 unconditionally to ensure the driver can still
build.

Fixes: a31b4dcf188c ("clk: davinci: remove support for da830")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>