Correct value for BN_security_bits()
Correct value for BN_security_bits()

The function BN_security_bits() uses the values from SP800-57 to assign
security bit values for different FF key sizes. However the value for 192
security bits is wrong. SP800-57 has it as 7680 but the code had it as
7690.

Reviewed-by: Tim Hudson <eb0be8e447f673b41b10eda09d63cd72526b0a42@openssl.org>
Reviewed-by: Rich Salz <c04971a99e5a9ee80eaab4b1deb37e845b0bd697@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4546)

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