staging: sm750fb: Call iounmap() to free mapped bus memory

staging: sm750fb: Call iounmap() to free mapped bus memory

If ioremap_wc() fails, the code jumps to the "exit" label and forgets to
free the bus memory mapped into "sm750_dev->pvReg". Mapped bus memory must
always be freed by calling iounmap().

Call iounmap(sm750_dev->pvReg) when the above-mentioned failures happen.

The site of the missing iounmap() has been detected by Smatch.

Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Link: https://lore.kernel.org/r/20220402175655.31512-1-fmdefrancesco@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>