Read eeprom for pcie_bifurcation info.

Introduce new APIs to read PCIe Bifurcation info from
eeprom.
Introduced an API which constructs the eeprom path
to read from. Mocked the same API for testing.

Testing: Introduced new unit tests to validate the
new functionality. Tested the logic on a Izumi
machine and verified that eeprom is read successfully
and we got the bifurcation info correctly.

Change-Id: I3ac8aa031348fe49f6daeb6ac48a11f6cac48790
Signed-off-by: Vamsy Nooney <vamsyknooney@gmail.com>