fsi: core: Fix legacy minor numbering

The legacy minor numbering shifts the chip id too much,
resulting in ids that overlap with regular ids. Since there
are only 2 bits for 4 types, only shift the chip id by 2
to fit the legacy ids in their reserved space.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Link: https://lore.kernel.org/r/20230612195657.245125-10-eajames@linux.ibm.com


Signed-off-by: Joel Stanley <joel@jms.id.au>