undefined reference to `cdelay' in spiflash.c when integrated_main_ram_size is not zero but uses spiflash

[Qiang Du]

As of 2023.04 release tag, the cdelay() function call introduced by commit 118dd6e in spiflahs.c breaks the bios building process, when the SoC is not using external dram (i.e. integrated_main_ram_size is non-zero) but uses spiflash. This is because cdelay() is defined in sdram.c.

Typical error message:

 CC       boot.o
 CC       cmd_bios.o
 CC       cmd_mem.o
 CC       cmd_boot.o
 CC       cmd_i2c.o
 CC       cmd_spiflash.o
 CC       cmd_litedram.o
 CC       cmd_liteeth.o
 CC       cmd_litesdcard.o
 CC       cmd_litesata.o
 CC       sim_debug.o
 CC       main.o
 CC       bios.elf
/usr/lib/riscv64-unknown-elf/bin/ld: ../liblitespi/liblitespi.a(spiflash.o): in function `spiflash_erase_range':
/home/tools/litex/litex/litex/soc/software/liblitespi/spiflash.c:193: undefined reference to `cdelay'
collect2: error: ld returned 1 exit status

[enjoy-digital]

Thanks @duqiang for reporting, this is fixed with 200a1a1 (thanks to @AndrewD and @rtucker85).