There is checkpatch.pl script where You can check if You wrote code in your kernel module according to linux kernel style. 

However can I ignore warning message?

WARNING: quoted string split across lines
#974: FILE: fpgax67-core.c:974:
+               dev_err(&pdev->dev, "registration not done, driver is already "
+                                                       "registered\n");

If I don't split line I will have another warning that 80 characters is exceeded.

For sure I can ignore warnings about:

WARNING: struct  should normally be const
#998: FILE: fpgax67-core.c :998:
+int fpgax67_unregister(struct platform_device *pdev)

For sure all errors must be fixed like:

const char* tmp -> change to -> const char *tmp;

if(  => if (   #insert space

Generally I don't know how much warnings should I correct. If it is mandatory or only good practise and I can omit some if it doesn't make sense.