i2c: synquacer: Deal with optional PCLK correctly

ACPI boot does not provide clocks and regulators, but instead, provides
the PCLK rate directly, and enables the clock in firmware. So deal
gracefully with this.

Fixes: 5575014 ("i2c: synquacer: Fix an error handling path in synquacer_i2c_probe()")
Cc: stable@vger.kernel.org # v6.10+
Cc: Andi Shyti <andi.shyti@kernel.org>
Cc: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>

Author: ardbiesheuvel

drivers/i2c/busses/i2c-synquacer.c

@@ -550,12 +550,13 @@ static int synquacer_i2c_probe(struct platform_device *pdev)
 	device_property_read_u32(&pdev->dev, "socionext,pclk-rate",
 				 &i2c->pclkrate);
 
-	pclk = devm_clk_get_enabled(&pdev->dev, "pclk");
+	pclk = devm_clk_get_optional_enabled(&pdev->dev, "pclk");
 	if (IS_ERR(pclk))
 		return dev_err_probe(&pdev->dev, PTR_ERR(pclk),
 				     "failed to get and enable clock\n");
 
-	i2c->pclkrate = clk_get_rate(pclk);
+	if (pclk)
+		i2c->pclkrate = clk_get_rate(pclk);
 
 	if (i2c->pclkrate < SYNQUACER_I2C_MIN_CLK_RATE ||
 	    i2c->pclkrate > SYNQUACER_I2C_MAX_CLK_RATE)