sw64: fix VM_DATA_DEFAULT_FLAGS

Sunway inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I645T3



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SW64 is designed to be have non-executable data by default. However,
VM_EXEC was set in VM_DATA_DEFAULT_FLAGS, which makes stack executable
and increases security risk. In particular, it causes some tests to
fail.

Redefine VM_DATA_DEFAULT_FLAGS with VM_DATA_FLAGS_NON_EXEC to fix this
problem.

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