MIPS: SNI: Fix MIPS_L1_CACHE_SHIFT

Commit 930beb5a ("MIPS: introduce MIPS_L1_CACHE_SHIFT_<N>") forgot
to select the correct MIPS_L1_CACHE_SHIFT for SNI RM. This breaks non
coherent DMA because of a wrong allocation alignment.

Fixes: 930beb5a ("MIPS: introduce MIPS_L1_CACHE_SHIFT_<N>")
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

arch/mips/Kconfig

@@ -877,6 +877,7 @@ config SNI_RM
 	select I8253
 	select I8259
 	select ISA
+	select MIPS_L1_CACHE_SHIFT_6
 	select SWAP_IO_SPACE if CPU_BIG_ENDIAN
 	select SYS_HAS_CPU_R4X00
 	select SYS_HAS_CPU_R5000