crypto: ecc - delete a useless function declaration

mainline inclusion
from mainline-v5.13-rc1
commit fa07c1a3
category: bugfix
bugzilla: 173981
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=fa07c1a30be7144f5d3292208f5d58799c92189f



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This function declaration has been added in 'ecc_curve.h',
delete it in 'crypto/ecc.h'.

Fixes: 4e660291(crypto: ecdsa - Add support for ECDSA ...)
Signed-off-by: Meng Yu <yumeng18@huawei.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Mingqiang Ling <lingmingqiang@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>