Staging: quickstart: Fix compilation warning on 64 bit arch

acpi_size is u32 or u64 depending on architecture. Cast it to
unsigned long and use %lu for printing.

This fix following build warning:
drivers/staging/quickstart/quickstart.c: In function ‘quickstart_acpi_ghid’:
drivers/staging/quickstart/quickstart.c:212:5: warning: format ‘%u’ expects argument of type ‘unsigned int’, but argument 3 has type ‘acpi_size’ [-Wformat]

Signed-off-by: Szymon Janc <szymon@janc.net.pl>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>