Even though sony-laptop has code to handle the volume-up/volume-down 
keys they don't work.  Pressing volume-down gets treated as 
SONYPI_EVENT_PKEY_P1 and volume-up as SONYPI_EVENT_PKEY_P2.

This is because volume-down generates event 0x01 with data mask 0x05 and 
although the sonypi_volumeev table exists to handle this the table 
sonypi_pkeyev steals the event before it gets handled.

Re-ordering the entries in the table type3_events and fixing the bug in 
sonypi_volumeev (up and down were inverted) makes the volume keys work.

See attached patch.

The two remaining problems are:

1. the EJECT key is mapped to FN_E
2. the MUTE key (event 5f, 31) is mapped to nothing.   (Not to important 
as it turns the speaker off in hardware).