hmi: Fix incorrect error message
hmi: Fix incorrect error message

An error message was clearly copy-pasted from the register beforehand,
so fix.

Signed-off-by: Russell Currey <b5ebcef270cdc73fa0593440445c07a93ae1bccb@russell.cc>
Reviewed-by: Alistair Popple <e9adbcf81c8a36ccc628e09bc92d0e25e1c8e501@popple.id.au>
Reviewed-by: Andrew Donnellan <efc2d7c347a094a6ec1d918179e819039044c564@au1.ibm.com>
Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>

legoater/skiboot,stewart-ibm/skiboot,stewart-ibm/skiboot,mikey/skiboot,qemu/skiboot,legoater/skiboot,shenki/skiboot,legoater/skiboot,legoater/skiboot,open-power/skiboot,legoater/skiboot,open-power/skiboot,mikey/skiboot,shenki/skiboot,qemu/skiboot,open-power/skiboot,mikey/skiboot,open-power/skiboot,qemu/skiboot,open-power/skiboot,shenki/skiboot,qemu/skiboot,stewart-ibm/skiboot,shenki/skiboot,shenki/skiboot,qemu/skiboot