crossgcc: Upgrade MPFR from 4.2.0 to 4.2.1

Change-Id: I1fb3630bf5e8a56ddcf6102faffde568134accc9
Signed-off-by: Elyes Haouas <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/77375
Reviewed-by: Martin L Roth <gaumless@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

Documentation/releases/coreboot-4.22-relnotes.md

@@ -23,6 +23,7 @@ Update this document with changes that should be in the release notes.
 
 * Upgrade GMP from 6.2.1 to 6.3.0
 * Upgrade binutils from 2.40 to 2.41
+* Upgrade MPFR from 4.2.0 to 4.2.1
 
 ### Additional coreboot changes