sw64: remove unused members from pcb_struct

Sunway inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I56OLG



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Since we have removed hmcall swpctx invocations, some members of
struct pcb_struct become useless. This patch removes them to reduce
the struct size.

As a result, struct processor_state is simplified too.

Signed-off-by: He Sheng <hesheng@wxiat.com>
Signed-off-by: Gu Zitao <guzitao@wxiat.com>