Alexandru Gagniuc authored Aug 18, 2021 and Tom Rini committed Sep 14, 2021

We are not guaranteed to have the padding_pkcs_15_verify symbol since
commit 92c960bc ("lib: rsa: Remove #ifdefs from rsa.h"), and
commit 61416fe9 ("Kconfig: FIT_SIGNATURE should not select RSA_VERIFY")

The padding_algos only make sense with RSA verification, which can now
be disabled in lieu of ECDSA. In fact this will lead to build failures
because of the missing symbol mentioned earlier.

To resolve this, move the padding_algos to a linker list, with
declarations moved to rsa_verify.c. This is consistent with commit
6909edb4 ("image: rsa: Move verification algorithm to a linker list")

One could argue that the added #ifdef USE_HOSTCC is ugly, and should
be hidden within the U_BOOT_PADDING_ALGO() macro. However, this would
be inconsistent with the "cryptos" list. This logic for was not
previously explored:

Without knowledge of the U_BOOT_PADDING_ALGO() macro, its use is
similar to something being declared. However, should #ifndef
USE_HOSTCC be part ...