util: Include stdint.h in libdrm.h

What does this MR do and why?

This allows intel_clc to build without a dependence on libdrm (by setting system_has_kms_drm = false in meson.build).

util: Include stdint.h in libdrm.h

drmGetDevices2()'s first parameter is a uint32_t.

Fixes: e05abb13455 ("util: Add a simple no-op libdrm shim")

util: Provide DRM_DEVICE_GET_PCI_REVISION definition

This allows src/intel/dev/intel_device_info.c to build with libdrm
stubbed out.