i2c: axxia: eliminate kernel-doc warnings

Add kernel-doc for 'slave' and 'irq' in struct axxia_i2c_dev.
Drop kernel-doc notation ("/**") for static functions since they
are not usually documented with kernel-doc.

Prevents these kernel-doc warnings:

i2c-axxia.c:150: warning: Function parameter or member 'slave' not described in 'axxia_i2c_dev'
i2c-axxia.c:150: warning: Function parameter or member 'irq' not described in 'axxia_i2c_dev'
i2c-axxia.c:172: warning: Function parameter or member 'ns' not described in 'ns_to_clk'
i2c-axxia.c:172: warning: Function parameter or member 'clk_mhz' not described in 'ns_to_clk'
i2c-axxia.c:172: warning: No description found for return value of 'ns_to_clk'
i2c-axxia.c:271: warning: Function parameter or member 'idev' not described in 'axxia_i2c_empty_rx_fifo'
i2c-axxia.c:271: warning: No description found for return value of 'axxia_i2c_empty_rx_fifo'
i2c-axxia.c:303: warning: Function parameter or member 'idev' not described in 'axxia_i2c_fill_tx_fifo'

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/all/202310181049.Vo62moV1-lkp@intel.com/
Reviewed-by: Andi Shyti <andi.shyti@kernel.org>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

Author: rddunlap

drivers/i2c/busses/i2c-axxia.c

@@ -131,6 +131,8 @@
  * @i2c_clk: clock reference for i2c input clock
  * @bus_clk_rate: current i2c bus clock rate
  * @last: a flag indicating is this is last message in transfer
+ * @slave: associated &i2c_client
+ * @irq: platform device IRQ number
  */
 struct axxia_i2c_dev {
 	void __iomem *base;
@@ -165,7 +167,7 @@ static void i2c_int_enable(struct axxia_i2c_dev *idev, u32 mask)
 	writel(int_en | mask, idev->base + MST_INT_ENABLE);
 }
 
-/**
+/*
  * ns_to_clk - Convert time (ns) to clock cycles for the given clock frequency.
  */
 static u32 ns_to_clk(u64 ns, u32 clk_mhz)
@@ -263,7 +265,7 @@ static int i2c_m_recv_len(const struct i2c_msg *msg)
 	return (msg->flags & I2C_M_RECV_LEN) != 0;
 }
 
-/**
+/*
  * axxia_i2c_empty_rx_fifo - Fetch data from RX FIFO and update SMBus block
  * transfer length if this is the first byte of such a transfer.
  */
@@ -295,7 +297,7 @@ static int axxia_i2c_empty_rx_fifo(struct axxia_i2c_dev *idev)
 	return 0;
 }
 
-/**
+/*
  * axxia_i2c_fill_tx_fifo - Fill TX FIFO from current message buffer.
  * @return: Number of bytes left to transfer.
  */