9p: fix bad error path in conversion routines
Mariusz Kozlowski authored

When buf_check_overflow() returns != 0 we will hit kfree(ERR_PTR(err))
and it will not be happy about it.
Signed-off-by: default avatarMariusz Kozlowski <m.kozlowski@tuxland.pl>
Signed-off-by: default avatarEric Van Hensbergen <ericvh@gmail.com>
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