phy: brcm-sata: remove unused variable

The newly introduced calibrate function has a variable
that has never been used and needs to be removed to avoid
this harmless warning:

drivers/phy/broadcom/phy-brcm-sata.c: In function 'brcm_stb_sata_calibrate':
drivers/phy/broadcom/phy-brcm-sata.c:514:24: error: unused variable 'priv' [-Werror=unused-variable]

Fixes: 3e507769 ("phy: brcm-sata: Implement calibrate callback")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Tejun Heo <tj@kernel.org>