i2c: cadence: Remove unnecessary register reads

In the `cdns_i2c_mrecv()` function the CTRL register of the Cadence I2C
controller is written and read back multiple times. The register value does
not change on its own. So it is possible to remember the just written value
instead of reading it back from the hardware.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Michal Simek <michal.simek@amd.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

Author: larsclausen

drivers/i2c/busses/i2c-cadence.c

@@ -613,7 +613,7 @@ static void cdns_i2c_mrecv(struct cdns_i2c *id)
 
 	/* Determine hold_clear based on number of bytes to receive and hold flag */
 	if (!id->bus_hold_flag && id->recv_count <= CDNS_I2C_FIFO_DEPTH) {
-		if (cdns_i2c_readreg(CDNS_I2C_CR_OFFSET) & CDNS_I2C_CR_HOLD) {
+		if (ctrl_reg & CDNS_I2C_CR_HOLD) {
 			hold_clear = true;
 			if (id->quirks & CDNS_I2C_BROKEN_HOLD_BIT)
 				irq_save = true;
@@ -624,7 +624,7 @@ static void cdns_i2c_mrecv(struct cdns_i2c *id)
 	addr &= CDNS_I2C_ADDR_MASK;
 
 	if (hold_clear) {
-		ctrl_reg = cdns_i2c_readreg(CDNS_I2C_CR_OFFSET) & ~CDNS_I2C_CR_HOLD;
+		ctrl_reg &= ~CDNS_I2C_CR_HOLD;
 		/*
 		 * In case of Xilinx Zynq SOC, clear the HOLD bit before transfer size
 		 * register reaches '0'. This is an IP bug which causes transfer size