linux-user: Fix mips fp64 executables loading

If a program requires fr1, we should set the FR bit of CP0 control status
register and add F64 hardware flag. The corresponding `else if` branch
statement is copied from the linux kernel sources (see `arch_check_elf` function
in linux/arch/mips/kernel/elf.c).

Signed-off-by: Daniil Kovalev <dkovalev@compiler-toolchain-for.me>
Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Message-Id: <20230404052153.16617-1-dkovalev@compiler-toolchain-for.me>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>