procfs: fix unintended truncation of returned mapped address

procfs: fix unintended truncation of returned mapped address

Currently, proc_reg_get_unmapped_area truncates upper 32-bit of the
mapped virtual address returned from get_unmapped_area method in
pde->proc_fops due to the variable rv of signed integer on x86_64.  This
is too small to have vitual address of unsigned long on x86_64 since on
x86_64, signed integer is of 4 bytes while unsigned long is of 8 bytes.
To fix this issue, use unsigned long instead.

Fixes a regression added in commit c4fe24485729 ("sparc: fix PCI device
proc file mmap(2)").

Signed-off-by: HATAYAMA Daisuke <[email protected]>
Cc: Alexey Dobriyan <[email protected]>
Cc: David S. Miller <[email protected]>
Tested-by: Michael Holzheu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>