fs: fat: ratelimit the IO errors

In case the application is still issuing the requests after
the low-level driver is shutdown, IO errors are expected.
Ratelimit those errors with the default ratelimit to avoid
watchdog bark issue in some cases.

Change-Id: Ida436cbf1be9556f456652e72bc1dac508abd047
Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>