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. Currently, AT_L1I_X,
AT_L1D_X and AT_L2_X are present in glibc header, and sysconf syscall
could use them to get information of cache through AUX vector.

The result of 'getconf -a' as follows:
LEVEL1_ICACHE_SIZE 32768
LEVEL1_ICACHE_ASSOC 8
LEVEL1_ICACHE_LINESIZE 64
LEVEL1_DCACHE_SIZE 32768
LEVEL1_DCACHE_ASSOC 8
LEVEL1_DCACHE_LINESIZE 64
LEVEL2_CACHE_SIZE 2097152
LEVEL2_CACHE_ASSOC 32
LEVEL2_CACHE_LINESIZE 64

Signed-off-by: Zong Li <zong.li@sifive.com>
Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>
Reviewed-by: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

riscv: cacheinfo: Implement cache_get_priv_group with a generic ops structure

Implement cache_get_priv_group() that will make use of a generic ops
structure to return a private attribute group for custom cache info.

Using riscv_set_cacheinfo_ops() users can hook their own custom function
to return the private attribute group for cacheinfo. In future we can
add more ops to this generic ops structure for SOC specific cacheinfo.

Signed-off-by: Yash Shah <yash.shah@sifive.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>