sim-se: Correctly calculate next PC in clone
sim-se: Correctly calculate next PC in clone

The clone syscall doesn't propagate all state in the PCState object
when calculating the return PC of a newly created process. Instead of
creating a new PCState object from the next PC address, copy the old
PC and advance it.

Change-Id: Ice53831920bcb5d198865169ed2cca8d06e37cfe
Signed-off-by: Andreas Sandberg <c9f5686ee5bd561c93f9de79681eee75bfa7f36e@arm.com>
Cc: Giacomo Travaglini <8eef13a4f970e2e9372c8d26ad0737b760f99c02@arm.com>
Cc: Javier Setoain <8a74c80c43facd01396beb11de48539de054b1e9@arm.com>
Cc: Brandon Potter <0c4047814a967fe28855a3d9d73d9b4959444c57@amd.com>
Reviewed-on: https://gem5-review.googlesource.com/c/15417
Reviewed-by: Jason Lowe-Power <68c46a606457643eab92053c1c05574abb26f861@lowepower.com>
Maintainer: Brandon Potter <0c4047814a967fe28855a3d9d73d9b4959444c57@amd.com>

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