signal: Deliver all of the siginfo perf data in _perf

signal: Deliver all of the siginfo perf data in _perf

Don't abuse si_errno and deliver all of the perf data in _perf member
of siginfo_t.

Note: The data field in the perf data structures in a u64 to allow a
pointer to be encoded without needed to implement a 32bit and 64bit
version of the same structure.  There already exists a 32bit and 64bit
versions siginfo_t, and the 32bit version can not include a 64bit
member as it only has 32bit alignment.  So unsigned long is used in
siginfo_t instead of a u64 as unsigned long can encode a pointer on
all architectures linux supports.

v1: https://lkml.kernel.org/r/[email protected]
v2: https://lkml.kernel.org/r/20210503203814[email protected]
v3: https://lkml.kernel.org/r/20210505141101[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Reviewed-by: Marco Elver <[email protected]>
Signed-off-by: "Eric W. Biederman" <[email protected]>