Fix wrong unit of meminfo parser

[Bluemangoo]

meminfo shows data like these:

MemTotal:       30524188 kB
MemFree:         3695720 kB
MemAvailable:   20690088 kB
...

In bytesize::ByteSize::from_str, they will be parsed as KB(source of Unit::from_str, called in ByteSize::from_str).

impl str::FromStr for Unit {
    // ...
    fn from_str(unit: &str) -> Result<Self, Self::Err> {
        match () {
            // ...
            _ if unit.eq_ignore_ascii_case("k") | unit.eq_ignore_ascii_case("kb") => {
                Ok(Self::KiloByte)
            }
            // ...
        }
    }
}

Anyway, it is formatted in KiB instead of KB. Or rather, kB has always been KiB. But bytesize ignored cases(eq_ignore_ascii_case).

See sources of Linux kernel here

static void show_val_kb(struct seq_file *m, const char *s, unsigned long num)
{
	seq_put_decimal_ull_width(m, s, num << (PAGE_SHIFT - 10), 8);
	seq_write(m, " kB\n", 4);
}

Thanks for @Franklin-Qi to mentiond it in #389