i2c: amd-mp2: Unregister callback on adapter add failure

i2c: amd-mp2: Unregister callback on adapter add failure

amd_mp2_register_cb() stores the platform I2C context in the MP2 PCI
driver's callback table before the adapter is registered. If
i2c_add_adapter() fails, probe returns and devres frees the context,
but the PCI driver can still dereference the stale pointer from its IRQ
and system-sleep callbacks.

Unregister the callback before returning the adapter registration error.

Fixes: 529766e0a011 ("i2c: Add drivers for the AMD PCIe MP2 I2C controller")
Co-developed-by: Ijae Kim <ae878000@gmail.com>
Signed-off-by: Ijae Kim <ae878000@gmail.com>
Signed-off-by: Myeonghun Pak <mhun512@gmail.com>
Cc: <stable@vger.kernel.org> # v5.2+
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>
Link: https://lore.kernel.org/r/20260721144147.31150-1-mhun512@gmail.com