MAINTAINERS: Drop obsolete FPU EMULATOR section

MAINTAINERS: Drop obsolete FPU EMULATOR section

Commit

  823caa173884 ("x86/fpu: Remove the math-emu/ FPU emulation library")

removes the directory arch/x86/math-emu/, but misses to also remove the
MAINTAINERS section FPU EMULATOR.

As Bill Metzenthen is already mentioned in the CREDITS for his contribution
to the FPU emulator, just add the email address in the MAINTAINERS section
to the CREDITS and then drop the obsolete FPU EMULATOR section.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@redhat.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://patch.msgid.link/20260519034550.276316-1-lukas.bulwahn@redhat.com