xtensa: drop sysmem and switch to memblock

Memblock is the standard kernel boot-time memory tracker/allocator. Use
it instead of the custom sysmem allocator. This allows using kmemleak,
CMA and device tree memory reservation.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

xtensa: keep sysmem banks ordered in add_sysmem_bank

Rewrite add_sysmem_bank so that it keeps bank order and merges
adjacent/overlapping banks.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

xtensa: split bootparam and kernel meminfo

Bootparam meminfo is a bootloader ABI, kernel meminfo is for the kernel
bookkeeping, keep them separate. Kernel doesn't care of memory region
types, so drop the type field and don't pass it to add_sysmem_bank.
Move kernel sysmem structures and prototypes to asm/sysmem.h and sysmem
variable and add_sysmem_bank to mm/init.c

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>