net: ipa: move GSI error values into "gsi_reg.h"

The gsi_err_code and gsi_err_type enumerated types are values that
fields in the GSI ERROR_LOG register can take on.  Move their
definitions out of "gsi.c" and into "gsi_reg.h", alongside the
definition of the ERROR_LOG register offset and field symbols.

Drop the "_ERR" suffix in the names of the gsi_err_code members.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>