clk: staging: correct reference to config IOMEM to config HAS_IOMEM

clk: staging: correct reference to config IOMEM to config HAS_IOMEM

Commit 0a0a66c984b3 ("clk: staging: Specify IOMEM dependency for Xilinx
Clocking Wizard driver") introduces a dependency on the non-existing config
IOMEM, which basically makes it impossible to include this driver into any
build. Fortunately, ./scripts/checkkconfigsymbols.py warns:

IOMEM
Referencing files: drivers/staging/clocking-wizard/Kconfig

The config for IOMEM support is called HAS_IOMEM. Correct this reference to
the intended config.

Fixes: 0a0a66c984b3 ("clk: staging: Specify IOMEM dependency for Xilinx Clocking Wizard driver")
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Link: https://lore.kernel.org/r/20210817105404.13146-1-lukas.bulwahn@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>