intel: common: Fix non-MISRA compliant code v2

intel: common: Fix non-MISRA compliant code v2

This patch is used to fix remaining non compliant code for Intel
SoCFPGA's mailbox and sip driver. These changes include:
- Change non-interface required uint32_t into unsigned int
- Change non-negative variable to unsigned int
- Remove obsolete variable initialization to 0

Signed-off-by: Abdul Halim, Muhammad Hadi Asyrafi <muhammad.hadi.asyrafi.abdul.halim@intel.com>
Change-Id: I3a16c7621a5fc75eb614d97d72e44c86e7d53bf5