staging: vme_user: print more detailed infomation when an error occurs

staging: vme_user: print more detailed infomation when an error occurs

when the slave_get function pointer belongs to the struct vme_bridge
member is NULL, it prompts that the detailed function name
"vme_slave_set" equivalent to __func__ not supported.

it is similar to the vme_slave_get function:
when vme_bridge->slave_set function pointer is NULL to print detailed
function name by using __func__.

Signed-off-by: Piro Yang <piroyangg@gmail.com>
Link: https://lore.kernel.org/r/20231227154739.6951-1-piroyangg@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>