staging: comedi: jr3_pci: use struct jr3_block instead of jr3_t

`struct jr3_t` contains a single array member `block` of member type
`struct jr3_block`.  Rather than using pointers to `struct jr3_t`, just
use pointers to `struct jr3_block` instead and treat it as an array.
Replace the local variables `struct jr3_t __iomem *iobase` with `struct
jr3_block __iomem *block`.  Remove the definition of `struct jr3_t` as
it is no longer needed.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>