wl12xx: 1281/1283 support - New boot sequence

Boot sequence support FREF clock and TCXO clock.
WL128x has two clocks input - TCXO and FREF.
TCXO is the main clock of the device, while FREF is used to sync
between the GPS and the cellular modem.
Auto-detection checks where TCXO is 32.736MHz or 16.368MHz, in that
case the FREF will be used as the WLAN/BT main clock.

[Use clock enumeration as defined in linux/wl12xx.h; remove
unnecessary else block in wl128x_switch_fref; remove unnecessary
change in main.c; remove some unnecessary debug prints and comments;
fix potential use of uninitialized value (pll_config) -- Luca]

Signed-off-by: Shahar Levi <shahar_levi@ti.com>
Reviewed-by: Luciano Coelho <coelho@ti.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>