ARC: boot log: cut down on verbosity

The syscall ABI has long been fixed, so no need to call that out now.

Also, there's no need to print really fine details such as norm,
barrel-shifter etc. Those are given in a Linux enabled hardware config.
So now we print just 1 line for all optional "instruction" related
hardware features

|
| ISA Extn	: atomic ll64 unalign mpy[opt 9] div_rem

vs. 2 before

|
|ISA Extn	: atomic ll64 unalign
|		: mpy[opt 9] div_rem norm barrel-shift swap minmax swape

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>