eal/linux: fix Rx interrupt read error management

eal/linux: fix Rx interrupt read error management

In eal_intr_proc_rxtx_intr, negative value may be used as argument to
a function expecting a positive value. If 'read' returns EAGAIN as
example, the bytes_read updates to a negative value which continue
be passed as argument for the next 'read'.

Coverity issue: 107115

Function read(fd, &buf, bytes_read) returns a negative number.
Assigning: signed variable bytes_read = read.
CID 107115 (#1 of 1): Argument cannot be negative
(NEGATIVE_RETURNS) bytes_read is passed to a parameter
that cannot be negative.
    bytes_read = read(fd, &buf, bytes_read);

Fixes: c9f3ec1a0f3f ("eal/linux: add Rx interrupt control function")

Signed-off-by: Cunming Liang <cunming.liang@intel.com>
Acked-by: John McNamara <john.mcnamara@intel.com>
Acked-by: David Marchand <david.marchand@6wind.com>