eeprom: starfive: Correct get_pcb_revision_from_eeprom()

pcb_revision is stored in the pcb_revision field of ATOM4. Correct it.
Move the function description to the header file.
Return 0 instead of 0xFF if read_eeprom() fails.

Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Fixes: aea1bd95b6 ("eeprom: starfive: Enable ID EEPROM configuration")
Signed-off-by: Hal Feng <hal.feng@starfivetech.com>

arch/riscv/include/asm/arch-jh7110/eeprom.h

@@ -9,6 +9,11 @@
 
 #include <linux/types.h>
 
+/**
+ * get_pcb_revision_from_eeprom() - get the PCB revision
+ *
+ * @return: the PCB revision or 0 on error.
+ */
 u8 get_pcb_revision_from_eeprom(void);
 
 /**

board/starfive/visionfive2/visionfive2-i2c-eeprom.c

@@ -535,19 +535,12 @@ int mac_read_from_eeprom(void)
 	return 0;
 }
 
-/**
- * get_pcb_revision_from_eeprom - get the PCB revision
- *
- * 1.2A return 'A'/'a', 1.3B return 'B'/'b',other values are illegal
- */
 u8 get_pcb_revision_from_eeprom(void)
 {
-	u8 pv = 0xFF;
-
 	if (read_eeprom())
-		return pv;
+		return 0;
 
-	return pbuf.eeprom.atom1.data.pstr[6];
+	return pbuf.eeprom.atom4.data.pcb_revision;
 }
 
 u8 get_ddr_size_from_eeprom(void)