riscv: Add cache information in AUX vector

There are no standard CSR registers to provide cache information, the
way for RISC-V is to get this information from DT. sysconf syscall
could use them to get information of cache through AUX vector.

The result of 'getconf -a|grep -i cache' as follows:
LEVEL1_ICACHE_SIZE                 32768
LEVEL1_ICACHE_ASSOC                2
LEVEL1_ICACHE_LINESIZE             64
LEVEL1_DCACHE_SIZE                 32768
LEVEL1_DCACHE_ASSOC                4
LEVEL1_DCACHE_LINESIZE             64
LEVEL2_CACHE_SIZE                  524288
LEVEL2_CACHE_ASSOC                 8
LEVEL2_CACHE_LINESIZE              64
LEVEL3_CACHE_SIZE                  4194304
LEVEL3_CACHE_ASSOC                 16
LEVEL3_CACHE_LINESIZE              64
LEVEL4_CACHE_SIZE                  0
LEVEL4_CACHE_ASSOC                 0
LEVEL4_CACHE_LINESIZE              0

Signed-off-by: Greentime Hu <greentime.hu@sifive.com>
Signed-off-by: Zong Li <zong.li@sifive.com>
Suggested-by: Zong Li <zong.li@sifive.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20220913061817.22564-8-zong.li@sifive.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>