FROMLIST: [PATCH 1/6] arm64: compat: Use vDSO sigreturn trampolines if available

(cherry pick from url https://patchwork.kernel.org/patch/10060449/

)

If the compat vDSO is enabled, it replaces the sigreturn page.
Therefore, we use the sigreturn trampolines the vDSO provides instead.

Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
Signed-off-by: Mark Salyzyn <salyzyn@android.com>
Bug: 63737556
Bug: 20045882
Change-Id: Ic0933741e321e1bf66409b7e190a776f12948024