libc: add EILSEQ for use in reporting checksum failure.
libc: add EILSEQ for use in reporting checksum failure.

This code is commonly used in the Linux kernel for reporting a
retryable error like a failed CRC.  This name and value is already
present in Linux and newlib.

Signed-off-by: Michael Hope <c71d7810e3c04e4d6ad9df326b82536b86a1bfbc@google.com>

mbolivar/zephyr,zephyriot/zephyr,mbolivar/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,kraj/zephyr,punitvara/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,galak/zephyr,punitvara/zephyr,explora26/zephyr,Vudentz/zephyr,nashif/zephyr,galak/zephyr,GiulianoFranchetto/zephyr,zephyriot/zephyr,kraj/zephyr,Vudentz/zephyr,punitvara/zephyr,punitvara/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,ldts/zephyr,ldts/zephyr,punitvara/zephyr,zephyriot/zephyr,zephyriot/zephyr,mbolivar/zephyr,ldts/zephyr,galak/zephyr,finikorg/zephyr,finikorg/zephyr,explora26/zephyr,explora26/zephyr,kraj/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,mbolivar/zephyr,Vudentz/zephyr,zephyriot/zephyr,ldts/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,mbolivar/zephyr,kraj/zephyr,explora26/zephyr,GiulianoFranchetto/zephyr,GiulianoFranchetto/zephyr,kraj/zephyr,Vudentz/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,finikorg/zephyr,ldts/zephyr,explora26/zephyr,galak/zephyr