fdk-aac: Disable for MIPS I, II, III and IV

This package uses the 'msub' instruction which is available only in
mips32 and mips64 ISAs.

[Thomas: replicate the new dependency to the comment.]

Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>