dtc: Simplify error handling for unparseable input

Currently, main() tests if it got a valid input tree from whichever
dt_from_*() function it invoked and if not, die()s.  For one thing,
this test has, for no good reason, three different ways for those
functions to communicate a failure to provide input (bi NULL, bi->dt
NULL, or bi->error non-zero).  For another, in every case save one, if
the dt_from_*() functions are unable to provide input they will
immediately die() (with a more specific error message) rather than
proceeding to the test in main().

Therefore, this patch removes this test, making the one case that
could have triggered it (in dt_from_source()) call die() directly
instead.  With this change, the error field in struct boot_info is now
unused, so remove it.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
4 files changed