Fix warnings in coreboot utilities.

Fix warnings in coreboot utilities.

- Fix some poor programming practice (breaks of strict aliasing as well
  as not checking the return value of read)
- Use PRIx64 instead of %llx to prevent compilation warnings with both
  32bit and 64bit compilers
- Use same compiler command options when linking inteltool and when
  detecting libpci for inteltool

Change-Id: I08b2e8d1bbc908f6b1f26d25cb3a4b03d818e124
Signed-off-by: Stefan Reinauer <reinauer@google.com>
Reviewed-on: http://review.coreboot.org/752
Tested-by: build bot (Jenkins)
Reviewed-by: Mathias Krause <minipli@googlemail.com>