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

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 / litex

undefined reference to `cdelay' in spiflash.c when integrated_main_ram_size is not zero but uses spiflash #1701