ocxl: Fix misleading comment

In ocxl_context_free() we note that the AFU reference we're releasing
was taken in "ocxl_context_init", a function that no longer exists.

Fix it to say ocxl_context_alloc() instead, which is the new name for
ocxl_context_init(), since it was renamed.

Fixes: b9721d27 ("ocxl: Allow external drivers to use OpenCAPI contexts")
Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
Acked-by: Frederic Barrat <fbarrat@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200226043923.5481-1-ajd@linux.ibm.com