remoteproc: Fixup coredump debugfs disable request

Fix the discrepancy observed between accepted input and read back value
while disabling remoteproc coredump through the coredump debugfs entry.

Fixes: 3afdc59e ("remoteproc: Add coredump debugfs entry")
Cc: stable@vger.kernel.org
Signed-off-by: Sibi Sankar <sibis@codeaurora.org>
Link: https://lore.kernel.org/r/20200916145100.15872-1-sibis@codeaurora.org


Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>