RFR(S) 8236251: ARM32: build failure after JDK-8234794

[Boris Ulasevich]

Hi,

The Metaspace::reserve_space function implementation was put inside LP64 
conditional block, but it is used in generic code, so it leads to 32-bit 
platforms build failure. With the fix I move the implementation out of 
#ifdef block.

http://cr.openjdk.java.net/~bulasevich/8236251/webrev.00
http://bugs.openjdk.java.net/browse/JDK-8236251

ARM32 build and smoke tests are OK.

thanks,
Boris