ARM: cti: fix manipulation of debug lock registers

The LOCKSTATUS register for memory-mapped coresight devices indicates
whether or not the device in question implements hardware locking. If
not, locking is not present (i.e. LSR.SLI == 0) and LAR is write-ignore,
so software doesn't actually need to check the status register at all.

This patch removes the broken LSR checks.

Cc: Ming Lei <ming.lei@canonical.com>
Reported-by: Mike Williams <michael.williams@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>