env: Rename setenv() to env_set()

We are now using an env_ prefix for environment functions. Rename setenv()
for consistency. Also add function comments in common.h.

Suggested-by: Wolfgang Denk <wd@denx.de>
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/mach-socfpga/misc_gen5.c b/arch/arm/mach-socfpga/misc_gen5.c
index 49b26b3..2f1da74 100644
--- a/arch/arm/mach-socfpga/misc_gen5.c
+++ b/arch/arm/mach-socfpga/misc_gen5.c
@@ -219,9 +219,9 @@
 {
 	const u32 bsel = readl(&sysmgr_regs->bootinfo) & 0x7;
 	const int fpga_id = socfpga_fpga_id(0);
-	setenv("bootmode", bsel_str[bsel].mode);
+	env_set("bootmode", bsel_str[bsel].mode);
 	if (fpga_id >= 0)
-		setenv("fpgatype", socfpga_fpga_model[fpga_id].var);
+		env_set("fpgatype", socfpga_fpga_model[fpga_id].var);
 	return socfpga_eth_reset();
 }
 #endif