spi: zynq: Use variable to remove u32 to u64 conversions

spi: zynq: Use variable to remove u32 to u64 conversions

Current code generates warning when it is compiled for arm64:
Warnings:
In file included from drivers/spi/zynq_spi.c:14:0:
drivers/spi/zynq_spi.c: In function ‘zynq_spi_init_hw’:
drivers/spi/zynq_spi.c:95:9: warning: large integer implicitly truncated
to unsigned type [-Woverflow]
  writel(~ZYNQ_SPI_ENR_SPI_EN_MASK, &regs->enr);
         ^
./arch/arm/include/asm/io.h:146:34: note: in definition of macro
‘writel’
 #define writel(v,c) ({ u32 __v = v; __iowmb(); __arch_putl(__v,c); __v;
})
                                  ^
drivers/spi/zynq_spi.c: In function ‘zynq_spi_release_bus’:
drivers/spi/zynq_spi.c:177:9: warning: large integer implicitly
truncated to unsigned type [-Woverflow]
  writel(~ZYNQ_SPI_ENR_SPI_EN_MASK, &regs->enr);
         ^
./arch/arm/include/asm/io.h:146:34: note: in definition of macro
‘writel’
 #define writel(v,c) ({ u32 __v = v; __iowmb(); __arch_putl(__v,c); __v;
})
                                  ^
This patch is using one variable to do conversion via u32 variable.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Jagan Teki <jteki@openedev.com>