docs: replace `-hda` with `-drive` & update `root=` kernel parameter

docs: replace `-hda` with `-drive` & update `root=` kernel parameter

According to QEMU manual:

Older options like `-hda` are essentially macros which expand into
`-drive` options for various drive interfaces. The original forms
bake in a lot of assumptions from the days when QEMU was emulating a
legacy PC, they are not recommended for modern configurations.

Signed-off-by: Integral <integral@archlinuxcn.org>
Reviewed-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>