spi: Remove unused/unnecessary spi_init function definitions

Remove spi_init definitions which:
1. Do nothing
2. Set static global variables to 0

Change-Id: If4c0cdbe2271fc7561becd87ad3b96bd45e77430
Signed-off-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-on: https://review.coreboot.org/20039
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Philippe Mathieu-Daudé <philippe.mathieu.daude@gmail.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

src/soc/imgtec/pistachio/spi.c

@@ -410,13 +410,6 @@ static int spim_io(const struct spi_slave *slave, struct spim_buffer *first,
 	return SPIM_OK;
 }
 
-/* Initialization, must be called once on start up */
-void spi_init(void)
-{
-	/* Clear everything just in case */
-	memset(img_spi_slaves, 0, sizeof(img_spi_slaves));
-}
-
 /* Claim the bus and prepare it for communication */
 static int spi_ctrlr_claim_bus(const struct spi_slave *slave)
 {

src/soc/qualcomm/ipq40xx/spi.c

@@ -201,12 +201,6 @@ static void spi_reset(struct ipq_spi_slave *ds)
 
 static struct ipq_spi_slave spi_slave_pool[2];
 
-void spi_init(void)
-{
-	/* just in case */
-	memset(spi_slave_pool, 0, sizeof(spi_slave_pool));
-}
-
 static struct ipq_spi_slave *to_ipq_spi(const struct spi_slave *slave)
 {
 	struct ipq_spi_slave *ds;

src/soc/qualcomm/ipq806x/spi.c

@@ -493,12 +493,6 @@ static const struct gsbi_spi spi_reg[] = {
 };
 static struct ipq_spi_slave spi_slave_pool[2];
 
-void spi_init()
-{
-	/* just in case */
-	memset(spi_slave_pool, 0, sizeof(spi_slave_pool));
-}
-
 static struct ipq_spi_slave *to_ipq_spi(const struct spi_slave *slave)
 {
 	struct ipq_spi_slave *ds;

src/soc/samsung/exynos5420/spi.c

@@ -95,10 +95,6 @@ static void spi_sw_reset(struct exynos_spi *regs, int word)
 	setbits_le32(&regs->ch_cfg, SPI_RX_CH_ON | SPI_TX_CH_ON);
 }
 
-void spi_init(void)
-{
-}
-
 static void exynos_spi_init(struct exynos_spi *regs)
 {
 	// Set FB_CLK_SEL.

src/southbridge/amd/sb700/spi.c

@@ -35,11 +35,6 @@ static uint32_t get_spi_bar(void)
 	return pci_read_config32(dev, 0xa0) & ~0x1f;
 }
 
-void spi_init(void)
-{
-	/* Not needed */
-}
-
 static void reset_internal_fifo_pointer(void)
 {
 	uint32_t spibar = get_spi_bar();