efi: earlycon: Reprobe after parsing config tables

Commit 732ea9db ("efi: libstub: Move screen_info handling to common
code") reorganized the earlycon handling so that all architectures pass
the screen_info data via a EFI config table instead of populating struct
screen_info directly, as the latter is only possible when the EFI stub
is baked into the kernel (and not into the decompressor).

However, this means that struct screen_info may not have been populated
yet by the time the earlycon probe takes place, and this results in a
non-functional early console.

So let's probe again right after parsing the config tables and
populating struct screen_info. Note that this means that earlycon output
starts a bit later than before, and so it may fail to capture issues
that occur while doing the early EFI initialization.

Fixes: 732ea9db ("efi: libstub: Move screen_info handling to common code")
Reported-by: Shawn Guo <shawn.guo@linaro.org>
Tested-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>