Revert "posix: device_io: require a full libc for c89 functions"

This reverts commit 6f62292.

PR zephyrproject-rtos#73978 introduced a regression.
Unfortunately this PR cannot be reverted without reverting also
Let's revert both PRs to stabilize main again towards the 3.7 release.

For more details on the issue see
zephyrproject-rtos#75205

Signed-off-by: Alberto Escolar Piedras <[email protected]>

Author: aescolar

lib/posix/options/Kconfig.device_io

@@ -8,7 +8,6 @@ config POSIX_DEVICE_IO
 	bool "POSIX device I/O [EXPERIMENTAL]"
 	select FDTABLE
 	select EXPERIMENTAL
-	select REQUIRES_FULL_LIBC
 	help
 	  Select 'y' here and Zephyr will provide an implementation of the POSIX_DEVICE_IO Option
 	  Group such as FD_CLR(), FD_ISSET(), FD_SET(), FD_ZERO(), close(), fdopen(), fileno(), open(),