Handle the difference timestamp count, got from drm_intel_reg_read.

Handle the difference timestamp count, got from drm_intel_reg_read.

In HSW and IVB, if x86_64 system, the low 32bits of timestamp count are stored in the high 32 bits of result which
got from drm_intel_reg_read, and 32-35 bits are lost; but in i386 system, the timestamp count match bspec.
It seems the kernel readq bug. So shift 32 bit in x86_64, and only remain 32 bits data in i386.

V2: In baytrail, don't have these issue, but need clear 32-35 bits.
Signed-off-by: Yang Rong <rong.r.yang@intel.com>
Reviewed-by: Zhigang Gong <zhigang.gong@linux.intel.com>