busybox

libbb: Converted safe_read to safe_write format

Changed safe_read to be symmetrical to safe_write, it shall
never return EINTR because it calls read multiple times,
the error is considered transient.

function                                             old     new   delta
safe_read                                             44      57     +13

Signed-off-by: Martin Lewis <martin.lewis.x84@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>