i5100_edac: connect fault injection to debugfs node

Create a debugfs direcotry i5100_edac/mcX for each memory controller and
add nodes to control how fault injection is preformed.

After configuring an injection using inject_channel, inject_deviceptr1,
inject_deviceptr2, inject_eccmask1, inject_eccmask2 and inject_hlinesel
trigger the injection by writing anything to inject_enable.

Example of a CE injection:

echo 0 > /sys/kernel/debug/i5100_edac/mc0/inject_channel
echo 1 > /sys/kernel/debug/i5100_edac/mc0/inject_hlinesel
echo 61440 > /sys/kernel/debug/i5100_edac/mc0/inject_eccmask1
echo 1 > /sys/kernel/debug/i5100_edac/mc0/inject_enable

Example of UE injection:

echo 0 > /sys/kernel/debug/i5100_edac/mc0/inject_channel
echo 2 > /sys/kernel/debug/i5100_edac/mc0/inject_hlinesel
echo 65535 > /sys/kernel/debug/i5100_edac/mc0/inject_eccmask1
echo 65535 > /sys/kernel/debug/i5100_edac/mc0/inject_eccmask2
echo 17 > /sys/kernel/debug/i5100_edac/mc0/inject_deviceptr1
echo 0 > /sys/kernel/debug/i5100_edac/mc0/inject_deviceptr2
echo 1 > /sys/kernel/debug/i5100_edac/mc0/inject_enable

Sometimes it is needed to enable the injection more then once (echo to
the inject_enable node) for the injection to happen, I am not sure why.

Signed-off-by: Niklas Söderlund <niklas.soderlund@ericsson.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>