ice: fix numeric overflow warning

When compiling and analyzing the driver on newer kernels, a static
analyzer warns about the following "numeric overflow" issues:

  "The result of expression: 'budget-1' generates 4-byte type while casting
   to a bigger size of 8-byte".

  "The result of expression: '*words-words_read' generates 4-byte type
   while casting to a bigger size of 8-byte".

Fix them both.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Signed-off-by: Anirudh Venkataramanan <anirudh.venkataramanan@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>