Fix default ZETA V2 SBC configuration

- Set the default CPUOSC to 8MHz (default value in the project's
  documentation), updated the User Guide
- Set the FDD controller to ZETA2 - regression introduced in bd664c3

Source/Doc/UserGuide.md

@@ -3353,7 +3353,7 @@ the RomWBW HBIOS configuration.
 | Interrupts        | Mode 2        |
 
  - CPU speed is detected at startup if DS1302 RTC is active
-   - Otherwise 20.000 MHz assumed
+   - Otherwise 8.000 MHz assumed
  - System timer is generated by onboard CTC
  - Hardware auto-detected:
    - Onboard DS1302 RTC

Source/HBIOS/Config/ZETA2_std.asm

@@ -26,7 +26,7 @@
 ;
 #include "cfg_zeta2.asm"
 ;
-CPUOSC		.SET	20000000	; CPU OSC FREQ IN MHZ
+CPUOSC		.SET	8000000		; CPU OSC FREQ IN MHZ
 INTMODE		.SET	2		; INTERRUPTS: 0=NONE, 1=MODE 1, 2=MODE 2
 CRTACT		.SET	TRUE		; ACTIVATE CRT (VDU,CVDU,PROPIO,ETC) AT STARTUP
 ;
@@ -35,7 +35,7 @@ UARTENABLE	.SET	TRUE		; UART: ENABLE 8250/16550-LIKE SERIAL DRIVER (UART.ASM)
 UARTSBC		.SET	TRUE		; UART: AUTO-DETECT SBC/ZETA ONBOARD UART
 ;
 FDENABLE	.SET	TRUE		; FD: ENABLE FLOPPY DISK DRIVER (FD.ASM)
-FDMODE		.SET	FDMODE_ZETA	; FD: DRIVER MODE: FDMODE_[DIO|ZETA|ZETA2|DIDE|N8|DIO3|RCSMC|RCWDC|DYNO|EPWDC]
+FDMODE		.SET	FDMODE_ZETA2	; FD: DRIVER MODE: FDMODE_[DIO|ZETA|ZETA2|DIDE|N8|DIO3|RCSMC|RCWDC|DYNO|EPWDC]
 ;
 PPIDEENABLE	.SET	FALSE		; PPIDE: ENABLE PARALLEL PORT IDE DISK DRIVER (PPIDE.ASM)
 SDENABLE	.SET	FALSE		; SD: ENABLE SD CARD DISK DRIVER (SD.ASM)