i2c: ocores: Fix pointer to integer cast warning

After commit a000b8c1 [i2c: ocores: Add support for the GRLIB port of the
controller and use function pointers for getreg and setreg function],
compiling i2c-ocores.c for 64-bit gives the following warning:

  drivers/i2c/busses/i2c-ocores.c: In function 'ocores_i2c_of_probe':
  drivers/i2c/busses/i2c-ocores.c:334:15: warning: cast from pointer to integer of different size

Fix it by casting the pointer to long.

Signed-off-by: Jayachandran C <jchandra@broadcom.com>
Acked-by: Peter Korsgaard <jacmet@sunsite.dk>
Acked-by: Andreas Larsson <andreas@gaisler.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>