Convert CONFIG_CMD_PCI to Kconfig

This converts the following to Kconfig:
   CONFIG_CMD_PCI

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
diff --git a/configs/boston32r2_defconfig b/configs/boston32r2_defconfig
index 6d93edc..dab3990 100644
--- a/configs/boston32r2_defconfig
+++ b/configs/boston32r2_defconfig
@@ -17,6 +17,7 @@
 # CONFIG_CMD_LOADB is not set
 # CONFIG_CMD_LOADS is not set
 # CONFIG_CMD_FPGA is not set
+CONFIG_CMD_PCI=y
 CONFIG_CMD_SNTP=y
 CONFIG_CMD_DNS=y
 CONFIG_CMD_LINK_LOCAL=y