sparc: Fix syscall fallback bugs in VDSO.

sparc: Fix syscall fallback bugs in VDSO.

BugLink: https://bugs.launchpad.net/bugs/1836654
[ Upstream commit 776ca1543b5fe673aaf1beb244fcc2429d378083 ]

First, the trap number for 32-bit syscalls is 0x10.

Also, only negate the return value when syscall error is indicated by
the carry bit being set.

Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>