i2c: cpm: Fix build break due to incompatible pointer types

commit 609d5a1b2b35bb62b4b3750396e55453160c2a17 upstream.

Since commit ea8daa7b9784 ("kbuild: Add option to turn incompatible
pointer check into error"), assignments from an incompatible pointer
types have become a hard error, eg:

  drivers/i2c/busses/i2c-cpm.c:545:91: error: passing argument 3 of
  'dma_alloc_coherent' from incompatible pointer type

Fix the build break by converting txdma & rxdma to dma_addr_t.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Cc: stable@kernel.org
Fixes: ea8daa7b9784
Signed-off-by: Willy Tarreau <w@1wt.eu>