ALSA: hda - Get back Input Source for ALC262 toshiba-s06 model

The commit f9e336f6
    ALSA: hda - Unify capture mixer creation in realtek codes
removed the "Input Source" mixer element creation for toshiba-s06 model
because it contains a digital-mic input.

This patch take the control back.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Cc: <stable@kernel.org>