libflash/ipmi-hiomap: Overhaul error handling

[ Upstream commit 64a6188 ]

The aim is to improve the robustness with respect to absence of the
BMC-side daemon. The current error handling roughly mirrors what was
done for the mailbox implementation, but there's room for improvement.

Errors are split into two classes, those that affect the transport state
and those that affect the window validity. From here, we push the
transport state error checks right to the bottom of the stack, to ensure
the link is known to be in a good state before any message is sent.
Window validity tests remain as they were in the hiomap_window_move()
and ipmi_hiomap_read() functions. Validity tests are not necessary in
the write and erase paths as we will receive an error response from the
BMC when performing a dirty or flush on an invalid window.

Recovery also remains as it was, done on entry to the blocklevel
callbacks. If an error state is encountered in the middle of an
operation no attempt is made to recover it on the spot, instead the
error is returned up the stack and the caller can choose how it wishes
to respond.

Cc: stable
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Signed-off-by: Stewart Smith <stewart@linux.ibm.com>
Signed-off-by: Vasant Hegde <hegdevasant@linux.vnet.ibm.com>