Replace all uses of 'EFI_CALL(func, params)' with
the expansion 'func(params)'.

Allows upcoming removal of eficall.h.

Adjust fwrandom() to return 0 for sucess, -1 for failure

Add support for the EFI Random Number Generator Protocol and use it to XOR
random data into the buffer that we feed the kernel.

ok deraadt@, mlarkin@