regulator: Fix formatting warnings in rpmh-regulator

Fix the following compiler warning from gcc 7.4.1 with -Werror enabled:

 drivers/regulator/rpmh-regulator.c:1285:3: error: format '%d' expects argument
   of type 'int', but argument 4 has type 'long int'
   aggr_vreg_err(aggr_vreg, "could not retrieve ARC aux data, rc=%d\n",

 drivers/regulator/rpmh-regulator.c:1292:3: error: format '%d' expects argument
   of type 'int', but argument 4 has type 'size_t {aka long unsigned int}'
   aggr_vreg_err(aggr_vreg, "more ARC levels defined than allowed: %d > %d\n",

 drivers/regulator/rpmh-regulator.c:1296:3: error: format '%d' expects argument
  of type 'int', but argument 4 has type 'size_t {aka long unsigned int}'
  aggr_vreg_err(aggr_vreg, "invalid ARC aux data size: %d\n",

Fixes: ff2723ac ("regulator: add rpmh-regulator driver")
Change-Id: Ic0dedbad2ea5a767dd4a56e55c231f3870342417
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>