ALSA: emu10k1: code refactoring

Partially restructures _snd_emu10k1_audigy_init_efx() and
_snd_emu10k1_init_efx() functions.

Be noted that the cast is demanded to use '__user'. So, in these cases,
avoid patches based on the coccinelle 'drop_kmalloc_cast' semantic patch.

Signed-off-by: Geyslan G. Bem <geyslan@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>