deblocker: Add a 'write' function
deblocker: Add a 'write' function

To support block writes, the deblocker should feature a 'write'
function, too. Since our only client that tries to use write
accesses so far (GRUB2) is always writing whole sectors, we
do not do the complicated read-modify-write dance here yet, but
simply check that the client always tries to write whole sectors.

Reviewed-by: Nikunj A Dadhania <e2f4a5db9b4735182a88051d1e7a3599f9eac9db@linux.vnet.ibm.com>
Signed-off-by: Thomas Huth <9e65be74847981e55b2564b6266c57d86d3bac05@redhat.com>
Signed-off-by: Alexey Kardashevskiy <ac1fc56530d7d037e1ea666f130daca22d72f964@ozlabs.ru>

open-power-host-os/slof,qemu/SLOF,qemu/SLOF,stefanberger/SLOF-tpm,stefanberger/SLOF-tpm,open-power-host-os/slof,aik/SLOF,aik/SLOF,open-power-host-os/slof,open-power-host-os/slof,stefanberger/SLOF-tpm,aik/SLOF,qemu/SLOF