net: phy: micrel: drop superfluous use of temp variable

'temp' was used before commit c0c99d0c

 ("net: phy: micrel: remove
the use of .ack_interrupt()") refactored the code. Now, we can simplify
it a little.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20230314124928.44948-1-wsa+renesas@sang-engineering.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>