fix crash in ecp_nistz256_point_add_affine()

fix crash in ecp_nistz256_point_add_affine()

The .rodata section with precomputed constant `ecp_nistz256_precomputed` needs to be
terminated by .text, because the ecp_nistz256_precomputed' happens to be the
first section in the file. The lack of .text makes code to arrive into the same
.rodata section where ecp_nistz256_precomputed is found. The exception is raised
as soon as CPU attempts to execute the code from read only section.

Fixes #24184

Reviewed-by: Paul Dale <ppzgs1@gmail.com>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/24192)