Fix uninitialized M when quick return in DLARRD and SLARRD

[akobotov]

Description
Quick return in DLARRD and SLARRD for N .LE. 0 happens too early, the output parameter M is left unset. This may lead to crash in ScaLAPACK's DLARRE2 and SLARRE2 respectfully, where the value returned in the M parameter is used to run a loop.

The fix:

1. Moves the zero initialization of M before deciding to quick return.
2. Removes duplicate initialization of INFO and duplicate check for quick return

Note

Most likely there are similar issues in other ?LARR? functions introduced on 16db9c2.

[langou]

Excellent contribution. Thanks. Yes, M should be set to 0 if N is 0. Great. Good fix. Thanks.

[langou]

I opened #770 so that we remember

Most likely there are similar issues in other ?LARR? functions introduced on 16db9c2

Any help is welcome.